Impact on Later Pregnancies

Thomas W. Strahan Memorial Library
Index
Standard of Care for Abortion
Abortion Decision-Making
Psychological Effects of Abortion
Social Effects and Implications
Physical Effects of Abortion
Abortion and Maternal Mortality
Adolescents and Abortion
Definition of Terms
Women's Health After Abortion
Material Yet to be Cataloged
Strahan Summary Articles

Sub-Index
Physical Effects
Abortion Technique Risks
Short Term Complications
Immediate Complications
Pain in Women
Organ or System Failure
Infections Related Complications
Impact on Later Pregnancies
Cancer Risks

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Secondary Infertility

Secondary Infertility due to Fetal Bone Retention A systematic literature review. Agolli A, Lawrence JA, Maskey U, Loh H, Parikh C. Sultan Qaboos Univ Med J. 2022 Nov;22(4):448-454.

Prolonged intrauterine retention of fetal bones during an abortion procedure can lead to secondary infertility. This review aimed to raise awareness among obstetric/gynaecologists about the possibility of this condition. A total of 17 case reports, seven case series and one retrospective study were included in this review, with 75 patients in total. Overall, 60% had a pregnancy termination in the second trimester, while 20% had a termination during the first trimester. Hysteroscopic resection was used to remove the intrauterine fetal bones in 69% of patients. In total, 59% of patients conceived following the procedure, 1% conceived despite the presence of intrauterine bones, 24% could not conceive at the time of the study and 16% had an unknown outcome. Transvaginal ultrasound was used for diagnosis in 41 (55%) patients, while pelvic ultrasound was used in 21 (28%) patients. In conclusion, secondary infertility is a common occurrence after a dilation and curettage procedure partially due to fetal bone retention. The gold standard for an accurate diagnosis and treatment is hysteroscopy.

One major pathway for infertility associated with abortion is through pelvic inflammatory disease, PID. Please read this second on PID.

"Role of Induced Abortion in Secondary Infertility," J.R. Daling, L.R. Spadoni, I. Emanuel, Obstet Gynecol 57: 59,1981.

A case-control study of married couples diagnosed as having secondary infertility at the University of Washington Hospital in 1976-78 found that women with a history of prior induced abortion had a 1.31 relative increased risk of secondary infertility (0.71-2.43, 95% C.I.), which was not statistically significant, compared with controls.

"Induced abortions, miscarriages and tobacco smoking as risk factors for secondary infertility," A. Tzonou, et al, J. Epidemiology and Comm. Health 47:36,1993.

In a case-control study by the Harvard Schools of Public Health and the University of Athens, of women in Athens, Greece in 1987-88, the occurrence of either induced abortions or spontaneous abortions independently and significantly increased the risk of subsequent secondary infertility. The logistic progression adjusted relative risks was 2.1 (1.1-4.0, 95% C.I.) for secondary infertility when there was 1 previous abortion and 2.3 (1.0-5.5, 95% C.I.) when there were 2 previous abortions. The adjusted relative risk of tobacco smoking for secondary infertility was 3.0 (1.3-6.8, 95% C.I.) compared to non- smokers. Secondary infertility was defined as [1] patient had a previous conception; [2] patient was married; [3] husband had a normal semen analysis and [4] patient had been trying become pregnant for at least 18 months.

"The effect of induced abortion on subsequent fertility," P Frank et al, Br J Obstetrics and Gynecology 100:575, 1993.

In a follow-up analysis of British women who had an induced abortion compared to women whose last pregnancy had a natural outcome, it was found that at the end of 12 months 89% of the abortion group had achieved a pregnancy compared to 93.3% on the non-abortion group which approached statistical significance

"Contraception after abortion and postpartum," H. Vorherr, Am.J. Obstet. Gynecol. 117(7):1002, Dec. 1, 1973

A study at the University of New Mexico reported that in 5-10% of healthy nonpostpartum women (apparently post abortion women) anovulary cycles are observed.

"Short and Long-term Results of Pregnancy by Different Methods, E.I," Sotnikova, Acta Medica Hungarica 43 (2): 139-143 (1986).

A Russian study of 560 women undergoing abortion by curettage, prostaglandin and vacuum aspiration found that one-third of the women had serious ovarian dysfunction 3-5 years post-abortion. Ovarian dysfunction was six times more observed than genital inflammations. Post-abortion complications were more frequent in women with a late menarche and with a history of genital inflammation. Instrumental abortion has more short-term complications (12%) than the other methods.

Uterine Fibroids

"Risk factors for uterine fibroids among women undergoing tubal sterilization," CR Chen et al, Am J Epidemiol 153(1): 20-26, 2001.

Parous women were at reduced risk for uterine fibroids while elective abortion did not reduce the risk for uterine fibroids compared to nulliparous women.

"Risk factors for uterine fibroids: reduced risk associated with oral contraceptives," RK Ross et al, British Medical Journal 293:359, August 9, 1986.

The risk of fibroids decreased consistently with increasing number of term pregnancies. There was no reduction in risk with incomplete pregnancies (induced abortion or spontaneous abortion) but a slight, but not significant increase in risk of fibroids.

Gestational Trophoblastic Disease

Gestational trophbloastic neoplasia includes complete hydatidiform mole, invasive mole, and choriocacinoma. Choriocarcinoma is malignant and therefore is considered a form of cancer. According to a 1986 U.S. study the incidence of choriocarcinoma is about 1 in 24,000 pregnancies. The incidence of molar pregnancy is reported to be 1 per 1500 live births and it is potentially life threatening. According to pregnancy-related deaths of U.S. women compiled by the CDC for 1987-90, 6 women died from molar pregnancy.

"Risk Factors for Gestational Tropoblastic Neoplasia," ML Messerli et al, Am J Obstet Gynecol 153:294, 1985.

A case-control study of gynecologic and reproductive risk factors for gestational trophoblastic neoplasia among Baltimore area women from 1975-1982 found that there was a higher mean incidence of induced abortions or spontaneous abortions among cases compared to controls, while women having at least one term pregnancy or one live birth provided a protective effect.

"A Case-Control Study from the People's Republic of China," LA Brinton et al, Am J Obstet Gynecol 161:121, 1989.

A case-control study of Chinese women with complete hydatidiform mole found that a history of a term birth was associated with a statistically significant reduced risk of 0.6 , while a history of one induced abortion had a nonsignificant increased relative risk of 1.2, and a history of two or more induced abortions had a statistically significant increased risk of 2.8, compared to women with no history of induced abortion.

"Risk factors for complete molar pregnancy from a case-control study," RS Berkowitz et al, Am J Obstet Gynecol 152:1016-1020, 1985.

A Massachusetts study of women with molar pregnancy matched with parous controls without molar pregnancy found that there was a 8-fold increased risk for molar pregnancy when the prior pregnancy was an induced abortion.

"Case-Control Study of Gestational Choriocarcinoma," JD Buckley et al, Cancer Research 48:1004-1010, 1981.

A multi-centered study of women with gestational choriocarcinoma matched women by year of pregnancy, age at pregnancy, and geographical residence found that an induced abortion preceding the choriocarcinoma was a risk factor while a live birth was protective against choriocarcinoma. The authors concluded that the most important factor for choriocarcinoma is the nature of the preceding pregnancy.

"Pregnancy Termination, Choricarcinoma Presenting as a Complication of Elective First Trimester Abortion," F.A. Lyon and L.L. Adcock, Minnesota Medicine, October, 1980, pp. 733-735.

A case report is presented in which metastatic gestational disease was detected at a routine two-week post abortion examination due to the incomplete removal of fetal remains.

"Choriocarcinoma Following M.T.P," A.S. Gupta, K. Mukherjee, S. Chowdhury, J. Indian Medical Association 82(7): 255, July, 1984.

Two cases are presented where choricarcinoma developed in Calcutta, India hospital following induced abortion.

Hypertension (High-Blood Pressure)

Subsequent risk of metabolic syndrome in women with a history of preeclampsia: data from the Health Examinees Study. Yang JJ, Lee SA, Choi JY, Song M, Han S, Yoon HS, Lee Y, Oh J, Lee JK, Kang D. J Epidemiol. 2015;25(4):281-8. doi: 10.2188/jea.JE20140136. Epub 2015 Mar 7.

"Women diagnosed with preeclampsia tended to be older at first pregnancy (25.4 years vs 24.9 years) and have higher rates of spontaneous (27.9% vs 23.3%) and artificial (71.2% vs 66.3%) abortions; these differences remained statistically significant after adjusting for potential confounders."

"Pregnancy-Related Mortality in the United States. 1987-1990," C.J. Berg et. al., Obstetrics and Gynecology 88:161,1996.

According to data published by the Centers for Disease Control for 1987-1990, 256 U.S. women died from complications due to pregnancy-induced hypertension out of a total number of 1453 pregnancy-related deaths during this period which represented 17.6% of all pregnancy-related deaths.

"The relationship between abortion in the first pregnancy and development of pregnancy-induced hypertension in the subsequent pregnancy," DM Strickland et al.,Am. J. of Obstet. Gynecol. 154: 146,1986.

In a study of 24,646 women who delivered at Parkland Memorial Hospital during 1977-80, the incidence of pregnancy-induced hypertension was 25.4% in primiaravid women, 22.3% among women whose only previous pregnancy terminated in abortion (either spontaneous or induced), and only 10% among women who carried two or more successive pregnancies to viability. Additional completed pregnancies after the first pregnancy did not confer any additional protective effect. It was concluded that the protective effect from abortion was small compared to a completed pregnancy.

"A Multivariate Analysis of Risk Factors for Preclampsia," B. Eskenazi et. al., JAMA 266: 231,1991.

A study of women who gave birth at Northern California Kaiser Permanent Hospital in 1984-85 found that women with a history of therapeutic abortion were 2.16 times more likely to have preclampsia (1.18-3.96, CI 95%) compared to no therapeutic abortion history. In contrast to induced abortion, a previous spontaneous abortion was found to have a protective effect (0.48, 0.24-0.95, CI 95%.)

"Pregnancy-Induced Hypertension in North Carolina," 1988 and 1989, D.A. Savitz, J. Zhang, Am. J. Public Health 82 (5): 675,1992.

A study of birth records in North Carolina during 1988-1989 examined the risk for pregnancy-induced hypertension (PIH) and found that the overall risk of PIH was 43.1 per 1000 births. Having had one child (Parity 1) was protective against PIH compared to no children (Parity 0) (0.4, 0.3-0.4, CI 95%). Blacks and whites were found to be a virtually equal risk. Mothers aged 35 or older were at increased risk compared to mothers aged 20-34 (1.6,1.4-1.8, CI 95%).

"Pre-eclampsia in second pregnancy," D.M. Campbell, I. MacGillivray, R. Carr-Hill, Br. J. Obstet. Gynaecol. 92: 131, Feb. 1985.

In a comprehensive and well-designed study of 29/851 women in Aberdeen, Scotland with first or second pregnancies, found that the incidence of proteinuric pre-clampsia after early abortion, which was either spontaneous or induced (separately studied) was similar to the population incidence in a first pregnancy (7.6% v. 5.6%). Only a pregnancy of 37 weeks gestation or more was likely to offer protection against pre-eclampsia in a second pregnancy. The incidence of proteinuric pre-eclampsia or mild pre-eclampsia in the next pregnancy after an induced abortion was 7.6% and 26.7% respectively in contrast to 1.9% and 17.0% where there was a viable first pregnancy prior to the second pregnancy.

Ectopic Pregnancy

"Risk of Ectopic Pregnancy and Previous Induced Abortion," C Tharaux-Deneux et al, Am J Public Health 88(3): 401, 1998.

A French case-control study found that among women with no previous ectopic pregnancy, women with one previous induced abortion had a statistically significant increased risk of 1.4, while women with two or more previous induced abortions had a statistically significant increased risk of 1.9 for ectopic pregnancy compared to women with no previous induced abortion. Ed Note: This study is possibly the only one which did not include women with a previous ectopic pregnancy. Previous ectopic pregnancy greatly increases the likelihood of another ectopic pregnancy and is a confounding factor. Failure to control for this variable would tend to make it appear that there was a lesser risk or perhaps no statistically increased risk of ectopic pregnancy from induced abortion.

"Risk Factors for Ectopic Pregnancy. A Population-Based Study," P.A. Marchbanks et. al, J. American Medical Association 259(12): 1823, March 25, 1988.

A case-control study at Mayo Clinic from 1935-1982, using univariate analysis found a 2.5 relative risk for ectopic pregnancy from induced abortion (1.02-6.1, 95% CI and a 4.0 relative risk from pelvic inflammatory disease (2.2-7.2, 95% CI. The Multivariate risk from induced abortion was 2.1 (0.8-5.9, 95% CI) and 3.3 (1.6-6.6, 95% CI for pelvic inflammatory disease.)

"An Updated Protocol for Abortion Surveillance With Ultrasound and Immediate Pathology," S.R. Goldstein, M. Danon, C. Watson, Obstet. Gynecol. 83: 55-58,1994.

In a study of 674 women who presented for first trimester abortion ultrasonography determined that 2.5% were 13 weeks or more despite bimanual examinations and the last menstrual period suggesting 12 or fewer weeks. The incidence of ectopic pregnancy was 0.58% and tubal pregnancy was 0.29% with an overall incidence of 0.87% using HCG and ultrasonography on-site testing.

"Induced abortions and risk of ectopic pregnancy," F. Parazzini et al. Human Reproduction 10(7): 1841,1995.

An Italian case-control study found that the multivariate risk of ectopic pregnancy for any induced abortion was 2.9,1.6-5.3, 95% CI. The risk increased with the number of induced abortions both with obstetric and non-obstetric controls.

"Ectopic Pregnancy Surveillance United States, 1970 - 1987," K. Nederof, H. Lawson, A. Saftlas, H. Atrash and E. Finch, Morbidity and Mortality Weekly Report 39(SS-4) December, 1990.

Ectopic pregnancy has risen from 17,800 cases in 1970 to 88,000 hospitalized cases in 1987. From 1970 - 1987 approximately 877,400 cases have been reported among U.S. women 15-44 years. Thirty women were reported to have died from ectopic pregnancy in 1987. Although the cause of ectopic pregnancy is unknown, it has been attributed to alteration in tubal motility, hormonal release and anatomical changes such as scarring. Scarring may be caused by acute and chronic salpingitis.

"Ectopic Pregnancy and Prior Induced Abortion," A.Levin, S. Schoenbaum, P. Stubblefield, S. Zimicki, R. Monson and K. Ryan, American Journal of Public Health, 72(3):253- 256, March 1982.

This study found a relationship between the number of prior induced abortions and the risk of ectopic pregnancy: the crude relative risk of ectopic pregnancy was 1.6 for women with one prior induced abortion and 4.0 for women with two or more prior induced abortions; however, use of multivariate techniques to control confounding factors reduced the relative risks to 1.3 and 2.6, respectively. The analysis suggests that induced abortion may be one of several risk factors for ectopic pregnancy, particularly for women who have had abortions plus pelvic inflammatory disease or multiple abortions.

"Pathogenesis of Tubal Pregnancy," J. Niles, and J. Clark, American Journal of Obstetrics and Gynecology, 105 (8): 1230-1234, December 15,1969.

A pathologic review was made of 436 ectopic pregnancies treated at a hospital over a 10 1/2 year period. Only about 40 percent of the cases studied had a histologic diagnosis of chronic inflammatory disease. Fifty-eight percent of the cases had no demonstrable histologic abnormality to produce an ectopic nidation, suggesting a functional pathogenesis. From the literature, the study noted factors which theoretically and logically could play a more important role in ectopic nidation than that of chronic pelvic inflammatory disease. They are (1) iatrogenic factors, (2) hormonal, (3) retrograde menstruation, (4) functional causes, and (5) the conceptus. Various studies were cited.

"Etiology of Ectopic Pregnancy: A New Concept," Joseph G. Asherman, Obstetrics and Gynecology, 16(6):619-624, December 1955.

Out of 325 patients with a history of ectopic pregnancy, 181 had one or more abortions, either spontaneous or induced. Of those, 135 were induced and 67 were spontaneous abortions. Twenty-one of the 181 women had both induced and spontaneous abortions. The study found that functional disturbances of the propelling mechanism of the tubes are to blame rather than pathologic changes in the tubes themselves. The movements of the tubal musculature (an inner circular and an outer longitudinal layer) are as dependent upon the hormonal as upon the nervous system. Any disturbance in the neurodendocrine balance is likely to bring about a change in the normal functioning of the tubes and may result in infertility or tubal pregnancy, depending on the severity of the disturbance. Why are induced abortions twice as damaging as spontaneous ones, when the intervention is the same for both? There is only one difference between the two kinds of abortion, the impact of psychic trauma. Any abortion, whether spontaneous or induced, may be the source of bitter frustration which will deepen with the passage of time if the yearning for motherhood is not satisfied. In induced abortion, however, an additional emotional factor is at work, leading, in the course of time, to a guilt complex. These make the inner tension of such women much higher than those experiencing spontaneous abortion.

"Ectopic Pregnancy and Myoma Uteri: Tetragenic Effects and Maternal characteristics," E. Matsunaga, and K. Shiota, Teratology 21: 61-69 (1980).

Fetal malformations were found in 11.6 percent of ectopic pregnancies compared with lesser percentages for controls. Maternal smoking and drinking were cited as causes.

"Induced Abortion and Ectopic Pregnancy in Subsequent Pregnancies," C.S. Chung, R.G. Smith, P.G. Steinoff, and M.P. Mi, American Journal of Epidemiology 115(6): 879- 887 (1982).

There was a clear association between the presence of post-abortion infection or retained parts and a 5 fold increase in ectopic pregnancy compared to uninfected women.

"Etiology of Cervical Pregnancy," D. Dicker, D. Feldbeg, N. Samuel, J.A. Goldman, The J. of Reproductive Medicine 30(1): 25, Jan., 1985.

An association was found between cervical pregnancy and prior induced abortion.

"Ectopic Pregnancy and First Trimester Abortion," L.A. Schonberg, Obstetrics and Gynecology 49(1) (Supp): 735, Jan. 1977.

Among a total of 41/753 first trimester abortions done over a 4 year period at two Planned Parenthood Centers in New York City from 1971-1975 only 11 verified cases of ectopic (tubal) pregnancy were discovered; 3 patients had a rupture of their tubal pregnancy immediately following suction curettage, 6 patients had rupture of the tube from 1-19 days after suction curettage. Only two unruptured ectopic gestations were diagnosed. Ed. Note: In 1975 the ectopic pregnancy rate was 7.6 per 1000 pregnancies (live births, induced abortions and ectopic pregnancy). Based on that rate PP should have discovered about 312 ectopic pregnancies.

"Ectopic Pregnancy in Relation to Previous Induced Abortion," T.R. Daling, W.H. Chow, N.S. Weiss, B.J. Metch and R. Suderstrom, Journal of the American Medical Association,253(7): 1005-1008, February 15,1985.

Women who have one induced abortion showed virtually no excess risk of ectopic pregnancy. (RR=1.4). For women with two or more abortions, the relative risk was 1.8. In the author's opinion, it remains unresolved whether having a legal induced abortion imparts an excess risk of ectopic pregnancy. Nonetheless, the results relating to the group of women having two or more abortions (RR of 1.8 and 2.6 in two of the studies) are worrisome.

"Risk Factors For Ectopic Pregnancy: A Case-Control Study in France, with Special Focus on Infectious Factors," J. Coste, N. Job-Spira, H. Fernandez, E. Papiernik, A. Spira, Am.J. Epidemiology 133(9): 839, May, 1991.

A case-control study in 1988 in seven Paris area hospitals found a 1.6 relative risk of ectopic pregnancy where there was prior induced abortion (1.1-2.3,95% C.I.). If adjustments were made for age, smoking and pelvic inflammatory disease the association disappeared. Ed. Note: Adjustments for PID and smoking should not have been made as induced abortion is implicated.

"Ectopic Pregnancy Critical Analysis of 139 Cases," M. Faith Kamsheh, Minnesota Medicine, February 1983, pp. 83-86.

Between 1975 and 1981, the number of ectopic pregnancies at Fairview Hospital more than doubled. Ectopic pregnancy is responsible for 10 percent of all maternal deaths. Patients who are infertile, did not use birth control, or who have a history of recent abortion or menstrual extraction, of PID, of IUD or recent removal of IUD or a history of previous tubal sterilization, tubal pregnancy, tubal reconstruction, and abdominal surgery have a high index of suspicion.

"Ectopic Pregnancy Case Study," Clinton A. Turner, Perspectives and Problems in OB/GYN, January 1985, Published for Stuart Pharmaceuticals by Communications in Med. Div. of Cahners Pub. Co., 475 Park Avenue S., New York, NY 10016.

The most alarming risk factor of all for ectopic pregnancy is a prior history of ectopic pregnancy. The risk of ectopic pregnancy in a patient who has had a prior one is approximately 20 times greater than that of a general population. A previous history of PID or a prior abortion were listed as risk factors for ectopic pregnancy.

"Ectopic Pregnancy - A New Surgical Epidemic," Louis Weinstein, M. Morris, D. Dotters and C.D. Christian, Obstetrics and Gynecology, 61(6): 698-701, June 1983

Between March 1972 and September 1981,154 patients were diagnosed for ectopic pregnancy at the University of Arizona. Currently, the incidence of ectopic pregnancy at the University of Arizona is one in 45 live births. 22.7 percent reported one or more previous therapeutic abortions; 14.9 percent reported a history of previous PID. Pelvic inflammatory disease is believed to be the major etiologic factor in the rising rate of ectopic pregnancy.

"Ectopic Pregnancy in the United States: 1970-1983," H. Atrash, Morbidity and Mortality Weekly Report 35(22S) Aug. 1986.

70,000 women were hospitalized for ectopic pregnancy in the U.S. in 1983, resulting in 70,000 fetal deaths. Ectopic pregnancy accounted for 12.8 percent of all maternal deaths in the U.S. in 1983. In 1985 black women continued to have a 3.5 times higher risk of death from ectopic pregnancy. Teenage black women have a 6.2 times higher risk than white teenagers.

"A 21-Year Survey of 654 Ectopic Pregnancies," James L. Breen, American Journal of Obstetrics and Gynecology, 106(7):1004-1019, April 1,1970

A review of the patients' operations or therapy seemed to substantiate that antecedent inflammatory disease recorded in 185 patients is a prime etiologic factor in ectopic pregnancy. A history of previous antibiotic therapy in 345 patients also implied therapy of pelvic inflammatory disease. A previous ectopic pregnancy in 45 patients (6.9 percent) or a previous tubal ligation in four patients (0.6 percent) may have been potentially edologic.

"An Overview of Infectious Aunts of Salpingitis, Their Biology and Recent Advances in Methods of Detection," P-A Mardh, American Journal Obstetrics and Gynecology, 138(7):933- 951 Part 2, December 1,1980.

In salpingitis, it is believed that anaerobic bacteria often gain entrance to the tubes as secondary invades from the lower genital tract in patients whose tubes have been damaged with sexually transmitted disease agents. In such secondary infections, both anaerobic and facultatively anaerobic bacteria can be demonstrated. Endogenous tubal infections may occur in hosts whose genital organs have been "compromised" by gynecologic surgery, curettage, legal or illegal abortion, or various diagnostic procedures. In the hospital catchment region of Lund such "iatrogenic" cases constitute approximately 15 percent of all salpingitis patients. See"Epidemiology. Etiology and Prognosis of Acute Salpingitis - a study of 1.457 laparoscopically verified cases," L. Westrom and P-A Mardh, in Non-gonococcal Urethritis and Related Infections, D. Hobson and K. Holmes, eds.,(Washington, D.C.: American Society for Microbiology, 1977) 84-90.

"Repeat Ectopic Pregnancy: A Study of 123 Consecutive Cases," Jack G. Hallatt, American Journal of Obstetrics and Gynecology, 122(4): 520, June 15,1975.

This study concludes the principal etiology of ectopic pregnancy as healed salpingitis which may have been gonorrheal, post-abortal or puerperal. These infections are readily controlled with antibiotics but fusion of the plical of the endosalpinix is a sequelae. These tubal adhesions subsequently trap the developing embryo.

"Chlamydia Trachomatis Infections in the United States, What Are They Costing Us?" A. Eugene Washington, R.E. Johnson, L.L. Sanders, Journal of the American Medical Association, 257(15): 2070-2072, April 17,1987.

It is estimated that each year 402,200 episodes of chlamydial PID occur, leading to 13,900 ectopic pregnancies and 280 deaths.

Sexually Transmitted Diseases. K.K. Holmes, P.A. Mardh, P.F. Sparling, O.J. Wiesner (1984) 630.

Women in the post-salpingitic state have a seven- to tenfold risk for ectopic pregnancy, compared with women who never had the disease.

Placenta Previa/Aburuptio Placentae/Retained Placenta

The risk factors associated with placenta previa: An umbrella review. Jenabi E, Salimi Z, Bashirian S, Khazaei S, Ayubi E. Placenta. 2022 Jan;117:21-27. doi: 10.1016/j.placenta.2021.10.009. Epub 2021 Oct 20. PMID: 34768164.

We evaluated in this umbrella review a systematic collection from meta-analyses conducted on risk factors associated with placenta previa. We searched PubMed, Scopus, and Web of Science until April 2021 assessing the risk factors associated with placenta previa. We calculated summary effect estimates odds ratio, relative risk, 95% CI, heterogeneity I2, 95% prediction interval, small-study effects, excess significance biases, and sensitive analysis. The quality of the meta-analyses was evaluated with AMSTAR 2. We included nine studies in the present umbrella review. Seven risk factors including prior induced abortion (OR 1·36, 95% CI: 1·02, 1·69), prior spontaneous abortion (OR 1·77, 95% CI: 1·60, 1·94), male fetus (OR 1·2, 95% CI: 1·2, 1·3), smoking (OR 1·42, 95% CI 1·30, 1·54) (RR 1·27, 95% CI: 1·18, 1·35) advanced maternal age (OR 3·16, 95% CI: 2·79, 3·57), cesarean (OR 1·60, 95% CI: 1·44, 1·76) and ART (singleton pregnancy) (RR 3·71, 95% CI: 2·67, 5·16) were graded as highly suggestive evidence (class III). Endometriosis (OR 3·03, 95% CI: 1·50, 6·13) and maternal cocaine use (OR 2·9, 95% CI: 1·9, 4·3) were graded as risk factors with weak evidence (class IV). This study provides suggestive evidence about prior spontaneous abortion, prior induced abortion, male fetus, smoking, advanced maternal age, cesarean section, and assisted reproductive techniques (singleton pregnancy) as risk factors associated with placenta previa.

"The Association of Placenta Previa with History of Caesarean Delivery and Abortion: A Meta Analysis," CV Anath et al, Am J Obstet Gynecol 177: 1071, 1997.

A review of 12 studies by researchers at the Robert Wood Johnson Medical School found that there was a strong association between a previous induced abortion and a higher risk of placenta previa among U.S. women.

"Placenta Previa in Relation to Induced and Spontaneous Abortion: A Population- Based Study," V.M. Taylor et al., Obstet. Gynecol. 82: 88-91,1993

A study of birth certificate data among Washington state white women during 1984-1987 found that women who reported one or more induced abortions were 1.28 times more likely to have a pregnancy complicated by placenta previa which was statistically significant.

"Induced Abortion: A Risk Factor For Placenta Previa," J.M. Barrett, F. H. Boehm, A.P. Killam, AmJ. Obstet Gynecol 141:769,1981.

A study at Vanderbilt University in 1979-80 found that 3.8% of the women with a history of induced abortion had placenta previa. If it was the first delivery since an induced first trimester induced abortion, the incidence of placenta previa was 4.6% compared to an overall percentage of 0.9%.

"Long-term sequelae following legally induced abortion," E.B. Obel, Danish Medical Bulletin 27(2): 61, April, 1980.

A Danish study compared women who's previous pregnancy was terminated by a legal induced abortion (group 1), with women whose previous pregnancy had ended in a spontaneous abortion or still birth (group 2), women whose previous pregnancy ended in a live birth (group 3), and women with no previous pregnancies. The study found that an induced abortion increases the risk of bleeding in a subsequent pregnancy compared with women with previous deliveries as well as women with no previous pregnancies. Delivery following a legally induced abortion had a greater tendency of retention of placenta or placental tissue than in a woman with no previous pregnancies. A legally induced abortion complicated by pelvic inflammatory disease may reduce a woman's fertility.

"Abruptio placentae and placenta previa: Frequency, perinatal mortality and cigarette smoking," R.L. Naeye, Obstet Gynecol. 55:701-704,1980.

Abruptio placentae and placenta previa was greater in women who smoked than in those who had never smoked. Perinatal mortality showed similar differences. Placenta previa became more frequent with age and with number of years smoked. Mothers who stopped smoking had a 23% lower frequency of abruptio placentae and a 33% lower frequency of placenta previa than women who continued to smoke during pregnancy.

"The conservative aggressive management of placenta previa," D.B. Cotton, J.A. Read, R.I.T. Paul, E.J. Quilligan, AmJ. Obstet.Gynecol. 137:687,1980.

A California study of 173 cases of placenta previa during 1975-78 found that a history of prior abortion, previous placenta previa or prior cesarean section enhanced the risk of developing placenta previa. The complications associated with placenta previa included fetal malpresentation (breech or transverse lie), cord prolapse and premature rupture of the membranes.

"Late Sequelae of Induced Abortion: Complications and Outcome of Pregnancy and Labor," S. Harlap and M. Davies, Am. J. Epidemiology 102(3): 217,1975.

A prospective study of 11,057 pregnancies of West Jerusalem mothers found that 0.3% of women reporting no previous induced abortions had placenta previa compared to 0.8% of women reporting one or more induced abortions according to crude rates. Standardized rates showed no statistical significance (0.4% vs. 0.5%).

"Risk Factors for Abruptio Placentae," M.A. Williams et. al.. Am. J. Epidemiology134: 965-972, 1991

A prior induced abortion was 1.3 times more likely to result in abruptio placente in a subsequent pregnancy compared to no prior induced abortion.

"The Impact of Multiple Induced Abortions on the Outcome of Subsequent Pregnancy," A. Lopes et. al., Aust NZ Obstet. Gynaecol. 31(1): 41,1991

In a study of Chinese women with two previous induced abortions and a subgroup of women with three or more previous induced abortions compared to age-matched primigravidas, the incidence of retained placenta was significantly higher among women with two prior induced abortions (2.9%) or three or more prior induced abortions (7.0%) compared with the control group (0.4%). Postpartum hemhorrage was also higher in women with two prior induced abortions (1.6%) or among women with three or more induced abortions (3.5%) compared with controls (0.8%).

Subsequent Miscarriage, Premature Birth or Low Birth Weight

Antidepressant use during pregnancy and risk of adverse neonatal outcomes: A comprehensive investigation of previously identified associations. Rommel AS, Momen NC, Molenaar NM, Agerbo E, Bergink V, Munk-Olsen T, Liu X. Acta Psychiatr Scand. 2022 Feb 12. doi: 10.1111/acps.13409. Epub ahead of print. PMID: 35152413.

Prenatal antidepressant exposure was associated with small decreases in gestational age and birthweight, as well as higher risk for moderate-to-late preterm birth, moderately low birthweight, neonatal admission and postnatal adaptation syndrome.

The duration of gestation at previous induced abortion and its impacts on subsequent births: A nationwide registry-based study. Kc S, Gissler M, Klemetti R. Acta Obstet Gynecol Scand. 2020 Mar 3. doi: 10.1111/aogs.13788. [Epub ahead of print]

INTRODUCTION: Previous induced abortions have been associated with adverse birth outcomes. However, only a few studies have considered the possible influence of gestational age at induced abortion. Therefore, this study aimed to identify the impacts of gestational age during prior induced abortion(s) on subsequent births among first-time mothers in Finland.

MATERIAL AND METHODS: First-time mothers (n = 418 690) with singleton births between 1996 and 2013 were identified from the Finnish Medical Birth Register and linked to the Abortion Register. Logistic regression analysis was used to estimate the risk (odds ratio [OR] and 95% confidence interval [CI]) of birth outcomes such as prematurity, low birthweight, perinatal death and small for gestational age (SGA).

RESULTS: Higher risk was determined for extremely preterm birth (OR 2.28; 95% CI 1.53-3.39) and very low birthweight (OR 1.62; 95% CI 1.22-2.16) in women having had late-induced abortion(s) (≥12 gestational weeks) compared with women having had early-induced abortion(s) (<12 gestational weeks); after adjusting for women's background characteristics, abortion method and interval between the pregnancies. When the analysis was limited to a single abortion, an increased risk was found for extremely preterm birth (OR 1.71; 95% CI 1.02-2.81). Higher risks were found for extremely preterm (OR 4.09; 95% CI 2.05-8.18) and very low birthweight (OR 2.65; 95% CI 1.61-4.35) among women with two or more late-induced abortions compared with those with two or more early-induced abortions. Worse outcomes were seen after a late-induced abortion compared to an early-induced abortion for both medically and surgically induced abortion.

CONCLUSIONS: The risk of subsequent adverse birth outcomes is very small if any, but the risk is higher with increasing gestational age at the time of induced abortion. Our study supports reduction of unintended pregnancy and offering abortion services without delay and as early in gestation as possible.

Pregnancy loss managed by cervical dilatation and curettage increases the risk of spontaneous preterm birth. McCarthy FP1, Khashan AS, North RA, Rahma MB, Walker JJ, Baker PN, Dekker G, Poston L, McCowan LM, O'Donoghue K, Kenny LC; SCOPE Consortium. Hum Reprod. 2013 Dec;28(12):3197-206. doi: 10.1093/humrep/det332. Epub 2013 Sep 19.

STUDY QUESTION: Do women with a previous miscarriage or termination of pregnancy have an increased risk of spontaneous preterm birth and is this related to previous cervical dilatation and curettage?

SUMMARY ANSWER: A single previous pregnancy loss (termination or miscarriage) managed by cervical dilatation and curettage is associated with a greater risk of SpPTB.

WHAT IS KNOWN ALREADY: Miscarriage affects ∼20% of pregnancies and as many as a further 20% of pregnancies undergo termination.

STUDY DESIGN, SIZE, DURATION: We utilized data from 5575 healthy nulliparous women with singleton pregnancies recruited to the Screening for Pregnancy Endpoints (SCOPE) study, a prospective cohort study performed between November 2004 and January 2011.

PARTICIPANTS/MATERIALS, SETTING, METHODS: The primary outcome was spontaneous preterm birth (defined as spontaneous preterm labour or preterm premature rupture of membranes (PPROM) resulting in preterm birth <37 weeks' gestation). Secondary outcomes included PPROM, small for gestational age, birthweight, pre-eclampsia and placental abruption.

MAIN RESULTS AND THE ROLE OF CHANCE: Women with previous pregnancy loss (miscarriage or termination) were compared with those with no previous pregnancy loss. There were 4331 (78%) women who had no previous pregnancy loss, 974 (17.5%) who had one early previous pregnancy loss, 249 (4.5%) who had two and 21 (0.5%) who had three or four losses. Women with two to four previous losses, but not those with a single loss, had an increased risk of spontaneous preterm birth (adjusted OR 2.12; 95% CI 1.55, 2.90) and/or placental abruption (adjusted OR 2.30; 95% CI 1.36, 3.89) compared with those with no previous pregnancy. A single previous miscarriage or termination of pregnancy where the management involved cervical dilatation and curettage was associated with an increased risk of spontaneous preterm birth (adjusted OR 1.64; 95% CI 1.08, 2.50; 6% absolute risk and adjusted OR 1.83; 95% CI 1.35, 2.48; 7% absolute risk, respectively) compared with those with no previous pregnancy losses. This is in contrast with women with a single previous miscarriage or termination managed non-surgically who showed no increase risk (adjusted OR 0.86; 95% CI 0.38, 1.94; 3.4% absolute risk and adjusted OR 0.87; 95% CI 0.69, 1.12; 3.8% absolute risk, respectively).

LIMITATIONS, REASONS FOR CAUTION: Although every effort was made to record accurate previous pregnancy data, it was not feasible to confirm the history and management of previous pregnancy loss by hospital records. This may have introduced recall bias.

WIDER IMPLICATIONS OF THE FINDINGS: This large prospective cohort study of healthy nulliparous women has demonstrated that women with either a previous miscarriage or termination of pregnancy were at increased risk of spontaneous preterm birth if they were managed by procedures involving cervical dilatation and curettage. However, overall, women with a single pregnancy loss did not have an increased risk of having any other of the adverse pregnancy outcomes examined. In contrast, two to four previous pregnancy losses were associated with an increased risk of having a pregnancy complicated by spontaneous preterm birth and/or placental abruption. Research is required to determine whether non-surgical management of miscarriage or termination of pregnancy should be advocated over surgical treatment.

Prior uterine evacuation of pregnancy as independent risk factor for preterm birth: a systematic review and metaanalysis Saccone G, Perriera L, Berghella V. Am J Obstet Gynecol. 2015 Dec 29. pii: S0002-9378(15)02596-X. doi: 10.1016/j.ajog.2015.12.044.

Background: Preterm birth (PTB) is the number one cause of perinatal mortality. Prior surgery on the cervix is associated with an increased risk of PTB. History of uterine evacuation, by either induced termination of pregnancy (I-TOP) or spontaneous abortion (SAB), which involve mechanical and/or osmotic dilatation of the cervix, has been associated with an increased risk of PTB in some studies but not in others.

Objective: The objective of the study was to evaluate the risk of PTB among women with a history of uterine evacuation for I-TOP or SAB.

Data Sources: Electronic databases (MEDLINE, Scopus, ClinicalTrials.gov, EMBASE, and Sciencedirect) were searched from their inception until January 2015 with no limit for language.

Study Eligibility Criteria: We included all studies of women with prior uterine evacuation for either I-TOP or SAB, compared with a control group without a history of uterine evacuation, which reported data about the subsequent pregnancy.

Study Appraisal and Synthesis Methods: The primary outcome was the incidence of PTB < 37 weeks. Secondary outcomes were incidence of low birthweight (LBW) and small for gestational age (SGA). We planned to assess the primary and the secondary outcomes in the overall population as well as in studies on I-TOP and SAB separately. The pooled results were reported as odds ratio (OR) with 95% confidence interval (CI).

Results: We included 36 studies in this metaanalysis (1,047,683 women). Thirty-one studies reported data about prior uterine evacuation for I-TOP, whereas 5 studies reported data for SAB. In the overall population, women with a history of uterine evacuation for either I-TOP or SAB had a significantly higher risk of PTB (5.7% vs 5.0%; OR, 1.44, 95% CI, 1.09–1.90), LBW (7.3% vs 5.9%; OR, 1.41, 95% CI, 1.22–1.62), and SGA (10.2% vs 9.0%; OR, 1.19, 95% CI, 1.01–1.42) compared with controls. Of the 31 studies on I-TOP, 28 included 913,297 women with a history of surgical I-TOP, whereas 3 included 10,253 women with a prior medical I-TOP. Women with a prior surgical I-TOP had a significantly higher risk of PTB (5.4% vs 4.4%; OR, 1.52, 95% CI, 1.08–2.16), LBW (7.3% vs 5.9%; OR, 1.41, 95% CI, 1.22–1.62), and SGA (10.2% vs 9.0%; OR, 1.19, 95% CI, 1.01–1.42) compared with controls. Women with a prior medical I-TOP had a similar risk of PTB compared with those who did not have a history of I-TOP (28.2% vs 29.5%; OR, 1.50, 95% CI, 1.00–2.25). Five studies, including 124,133 women, reported data about a subsequent pregnancy in women with a prior SAB. In all of the included studies, the SAB was surgically managed. Women with a prior surgical SAB had a higher risk of PTB compared with those who did not have a history of SAB (9.4% vs 8.6%; OR, 1.19, 95% CI, 1.03–1.37).

Conclusion: Prior surgical uterine evacuation for either I-TOP or SAB is an independent risk factor for PTB. These data warrant caution in the use of surgical uterine evacuation and should encourage safer surgical techniques as well as medical methods.

Note: The abstract is oddly worded, stating that women with a medically induced abortion "had a similar risk of PTB" when in fact the odds ratio reveals a 50% increased risk (1.5 times the normal rate, OR=1.50) which is very similar to that of surgical abortion (OR=1.52). The confidence interval for surgical abortions (CI, 1.08-2.16) is smaller than that for medical abortions (CI, 1.00-2.25) due to the larger number of women in the studies who had surgical abortions (913,297) compared to medical abortions (124,133). The confidence interval for medical abortions indicates that the "true" risk is most likely to lie somewhere between a 1 and 2.25 times the normal rate--meaning there is some small chance that there is zero increased risk (1 times the normal risk is just equal to the normal risk). But it is far more likely to be above 1 and even up to 2.25 times higher. In short, the dismissive "similar risk" claim is clearly intended to lend some support to the claims that medical abortion is safer than surgical abortion. But really, this study is telling us that the best evidence indicates that the odds ratio for increased risk of PTB following medically induced abortion (OR=1.50) is almost indistinguishable from that for surgical abortion (1.52).

Effect of induced abortions on early preterm births and adverse perinatal outcomes. Hardy G, Benjamin A, Abenhaim HA. J Obstet Gynaecol Can. 2013 Feb;35(2):138-43.

OBJECTIVES: To examine the association between prior induced abortions and prematurity and to explore potential mechanisms for a relationship, including second trimester pregnancy losses and infections.

METHODS: We conducted a retrospective review of the records of all women who delivered between April 2001 and March 2006 using data from the McGill Obstetric and Neonatal Database. Exposure was categorized as having had no prior induced abortions, one prior induced abortion, or two or more prior induced abortions. Our primary outcome was gestational age at delivery, categorized as < 24 weeks, < 26 weeks, < 28 weeks, < 32 weeks and < 37 weeks. Secondary outcomes were intrapartum fever, NICU admission, and use of tocolysis.

RESULTS: A total of 17 916 women were included in the study. Of these 2276 (13%) had undergone one prior induced abortion, and 862 (5%) had undergone two or more prior induced abortions. Women with a prior induced abortion were more likely to be smokers and to consume alcohol, and were less likely to be married. Women who reported one prior induced abortion were more likely to have premature births by 32, 28, and 26 weeks; adjusted odds ratios were 1.45 (95% CI 1.11 to 1.90), 1.71 (95% CI 1.21 to 2.42), and 2.17 (95% CI 1.41 to 3.35), respectively. This association was stronger for women with two or more previous induced abortions. Prior induced abortion was associated with an increased requirement for tocolysis in subsequent pregnancies, but there was no association between prior induced abortions and NICU admission, intrapartum fever, and preterm premature rupture of membranes.

CONCLUSION: Our study showed a significant increase in the risk of preterm delivery in women with a history of previous induced abortion. This association was stronger with decreasing gestational age.

Induced termination of pregnancy and low birth weight and preterm birth: a systematic review and meta-analysis. Shah P. et al. BJOG 2009;116(11):1425-1442.

Thirty-seven studies of low-moderate risk of bias were included. A history of one I-TOP was associated with increased unadjusted odds of LBW (OR 1.35, 95% CI 1.20-1.52) and PT (OR 1.36, 95% CI 1.24-1.50), but not SGA (OR 0.87, 95% CI 0.69-1.09). A history of more than one I-TOP was associated with LBW (OR 1.72, 95% CI 1.45-2.04) and PT (OR 1.93, 95% CI 1.28-2.71). Meta-analyses of adjusted risk estimates confirmed these findings.

Medical termination of pregnancy during the second versus the first trimester and its effects on subsequent pregnancy. Männistö J, Mentula M, Bloigu A, Gissler M4, Niinimäki M, Heikinheimo O.Contraception. 2013 Nov 6. pii: S0010-7824(13)00683-5. doi: 10.1016/j.contraception.2013.10.015.

Abstract

OBJECTIVE: The objective was to compare the risks of preterm birth, low birth weight, small for gestational age (SGA) infants and placental complications in subsequent pregnancy after second vs. first trimester medical termination of pregnancy (MTOP) in primigravid women.

STUDY DESIGN: A total of 88,522 women who underwent termination of pregnancy during 2000-2009 were identified using Finnish health registers. Of them, primigravid women who underwent MTOP and had subsequent pregnancy ending in live birth up to the end of 2009 (n=3843) were included in the study. The incidences and risks of preterm birth, low birth weight, SGA infants and placental complications after first- (n=3427) vs. second-trimester MTOP (n=416) were compared.

RESULTS: Differences between the study groups in the incidences of preterm birth (3.9% in both groups), low birth weight (3.9% in the second- vs. 3.2% in the first-trimester group), SGA infants (2.4% vs. 2.5%) and placental complications (1.9% vs. 2.6%) were statistically insignificant. Second-trimester MTOP was associated with similar risks of preterm birth, low birth weight, SGA infants and placental complications compared with first-trimester MTOP after adjustment for background characteristics. After second-trimester MTOP, 51.2% of women underwent surgical evacuation, and 4.3% were diagnosed with infection. The differences in the risks of preterm birth, low birth weight, SGA infants and placental complications were statistically insignificant between women with vs. without these complications following second-trimester MTOP.

CONCLUSIONS: Second-trimester MTOP among primigravid women did not increase the risks of preterm birth, low birth weight, SGA infants or placental complications in subsequent pregnancy compared with first-trimester MTOP.

Editor's Note: This study did not compare these adverse effects relative to primagravid women carrying a first pregancy to term.

Effect of Induced Abortions on Early Preterm Births and Adverse Perinatal Outcomes. J Obstet Gynaecol Can 2013;35(2):138–143.

Abstract excerpt

Results: A total of 17 916 women were included in the study. Of these 2276 (13%) had undergone one prior induced abortion, and 862 (5%) had undergone two or more prior induced abortions. Women with a prior induced abortion were more likely to be smokers and to consume alcohol, and were less likely to be married. Women who reported one prior induced abortion were more likely to have premature births by 32, 28, and 26 weeks; adjusted odds ratios were 1.45 (95% CI 1.11 to 1.90), 1.71 (95% CI 1.21 to 2.42), and 2.17 (95% CI 1.41 to 3.35), respectively. This association was stronger for women with two or more previous induced abortions. Prior induced abortion was associated with an increased requirement for tocolysis in subsequent pregnancies, but there was no association between prior induced abortions and NICU admission, intrapartum fever, and preterm premature rupture of membranes.

Conclusion: Our study showed a significant increase in the risk of preterm delivery in women with a history of previous induced abortion. This association was stronger with decreasing gestational age.

Editor's translation: One prior abortion increased the risk of premature delivery at 26 weeks or earlier by at least 41% up to 235%.

Repeated Abortion Affects Subsequent Pregnancy Outcomes in BALB/c Mice Lv F, Xu X, Zhang S, Wang L, Wang N, He B, Wang J. PLoS One. 2012;7(10):e48384. doi: 10.1371/journal.pone.0048384. Epub 2012 Oct 31.

Induced medical abortion using mifepristone (RU 486)in mice was associated with elevated rates of miscarriage, placental dysfunction, with reduced expression of tissue factor (TF) and genes encoding proteins involved in metabolic functions relevant to pregnancy, such as 11β-hydroxysteroid dehydrogenase 1/2 (11β-HSD1/2) and glucocorticoid receptor (GR). Reduced expression was also observed for platelet endothelial cell adhesion molecule-1 (CD31) and vascular endothelial growth factor (VEGF). In offspring from subsequent pregnancies, genes involved in lipid metabolism, which may enhance key lipid transcription factors, such as PPARA and PPARG, as well as GR/11β-HSD1, were downregulated in the liver. In addition, the sperm motility of the F1 males reduced.

This study is of particular note because it is the only known study using animals. Abortion procedures have generally been implemented on human beings without prior test on animals.

Contribution of Risk Factors to Extremely, Very and Moderately Preterm Births – Register- Based Analysis of 1,390,742 Singleton Births. Raisanen S, Gissler M, Saari J, Kramer M, Heinonen S (2013) PLoS ONE 8(4): e60660.

The study reported significantly elevated rates of extremely preterm, very preterm, and moderately preterm births for pregnancies among women with a history of abortion (adjusted odds ratios being 1.28, 1.16, 1.07, respectively, and for women who smoked ( 1.21, 1.23, 1.15.) The authors concluded that smoking was the most important risk, but they were unaware and did not discuss the link between abortion and elevated rates of smoking.

Birth outcomes after induced abortion: a nationwide register-based study of first births in Finland. Klemetti R, Gissler M, Niinimäki M, Hemminki E. Hum Reprod. 2012 Nov;27(11):3315-20. doi: 10.1093/humrep/des294. Epub 2012 Aug 29.

Abstract

STUDY QUESTION: Is the perinatal health of first-born children affected by the mother's previous induced abortion(s) (IAs)?

SUMMARY ANSWER: Prior IAs, particularly repeat IAs, are correlated with an increased risk of some health problems at first birth; even in a country with good health care quality.

WHAT IS KNOWN ALREADY: A positive association between IA and risk of preterm birth or a dose-response effect has been found in some previous studies. Limited information and conflicting results on other infant outcomes are available.

STUDY DESIGN, SIZE AND DURATION: Nationwide register-based study including 300 858 first-time mothers during 1996-2008 in Finland.

PARTICIPANTS/MATERIALS, SETTING AND METHODS: All the first-time mothers with a singleton birth (obtained from the Medical Birth Register) in the period 1996-2008 (n = 300 858) were linked to the Abortion Register for the period 1983-2008.

MAIN RESULTS AND THE ROLE OF CHANCE: Of the first-time mothers, 10.3% (n = 31 083) had one, 1.5% had two and 0.3% had three or more IAs. Most IAs were surgical (88%) performed before 12 weeks (91%) and carried out for social reasons (97%). After adjustment, perinatal deaths and very preterm birth (<28 gestational week) suggested worse outcomes after IA. Increased odds for very preterm birth were seen in all the subgroups and exhibited a dose-response relationship: 1.19 [95% confidence interval (CI) 0.98-1.44] after one IA, 1.69 (1.14-2.51) after two and 2.78 (1.48-5.24) after three IAs. Increased odds for preterm birth (<37 weeks) and low birthweight (<2500 g and <1500 g) were seen only among mothers with three or more IAs: 1.35 (1.07-1.71), 1.43 (1.12-1.84) and 2.25 (1.43-3.52), respectively.

LIMITATIONS, REASONS FOR CAUTION: Observational studies like ours, however large and well-controlled, will not prove causality.

WIDER IMPLICATIONS OF THE FINDINGS: In terms of public health and practical implications, health education should contain information of the potential health hazards of repeat IAs, including very preterm birth and low birthweight in subsequent pregnancies. Health care professionals should be informed about the potential risks of repeat IAs on infant outcomes in subsequent pregnancy.

Reproductive outcomes following induced abortion: a national register-based cohort study in Scotland. Bhattacharya S, Lowit A, Bhattacharya S, Raja EA, Lee AJ, Mahmood T, Templeton A. BMJ Open. 2012 Aug 6;2(4). pii: e000911. doi: 10.1136/bmjopen-2012-000911. Print 2012.

Abstract

OBJECTIVE: To investigate reproductive outcomes in women following induced abortion (IA).

DESIGN: Retrospective cohort study.

SETTING: Hospital admissions between 1981 and 2007 in Scotland.

PARTICIPANTS: Data were extracted on all women who had an IA, a miscarriage or a live birth from the Scottish Morbidity Records. A total of 120 033, 457 477 and 47 355 women with a documented second pregnancy following an IA, live birth and miscarriage, respectively, were identified.

OUTCOMES: Obstetric and perinatal outcomes, especially preterm delivery in a second ongoing pregnancy following an IA, were compared with those in primigravidae, as well as those who had a miscarriage or live birth in their first pregnancy. Outcomes after surgical and medical termination as well as after one or more consecutive IAs were compared.

RESULTS: IA in a first pregnancy increased the risk of spontaneous preterm birth compared with that in primigravidae (adjusted RR (adj. RR) 1.37, 95% CI 1.32 to 1.42) or women with an initial live birth (adj. RR 1.66, 95% CI 1.58 to 1.74) but not in comparison with women with a previous miscarriage (adj. RR 0.85, 95% CI 0.79 to 0.91). Surgical abortion increased the risk of spontaneous preterm birth compared with medical abortion (adj. RR 1.25, 95% CI 1.07 to 1.45). The adjusted RRs (95% CI) for spontaneous preterm delivery following two, three and four consecutive IAs were 0.94 (0.81 to 1.10), 1.06 (0.76 to 1.47) and 0.92 (0.53 to 1.61), respectively.

CONCLUSIONS: The risk of preterm birth after IA is lower than that after miscarriage but higher than that in a first pregnancy or after a previous live birth. This risk is not increased further in women who undergo two or more consecutive IAs. Surgical abortion appears to be associated with an increased risk of spontaneous preterm birth in comparison with medical termination of pregnancy. Medical termination was not associated with an increased risk of preterm delivery compared to primigravidae.

[http://www.ncfpc.org/FNC/1305-FNC-Spring13-Abortion%27sImpactOnPrematurity2.pdf Abortion’s Impact on Prematurity: Closing the Knowledge Gap] Martin McCaffrey, M.D.. Family North Carolina, 2013

A good summary of the literature.

Abortion 'increases risk of premature birth' 33%

Results of study presented at European Society of Human Reproduction and Embryology (ESHRE) conference in 2011 reported that women with a history of induced abortion were 33% more likely to have their next pregnancy delivered prematurely, and 44% more likely to give birth extremely prematurely, before 34 weeks. The study was led by Dr. Siladitya Bhattacharya, and examined the outcomes of the second pregnancies of 170,000 women who had previously had an abortion and 458,000 women undergoing their first pregnancies.

Induced Abortion and Risk of Later Premature Births. B Rooney and BC Calhoun, Journal of American Physicians and Surgeons 8(2):46-49, 2003.

This study summarizes 49 studies which have demonstrated a statistically significant risk in premature births among women with prior induced abortions.

"Obstetric Complications and Risk for Severe Psychopathology in Childhood" J Autism and Developmental Disorders (2001;31:279-285 ) Eaton WW, Mortensen PB, Thomsen PH, Frydenberg M.

Children born to women with prior history of induced abortion had 72% higher relative risk of later being diagnosed as mentally retarded, and a 40% greater risk of being diagnosed with a learning disorder, and a 47% risk of being diagnosed with some other psychological disorder.

Prenatal and perinatal risk factors for autism. J Perinat Med. 1999;27(6):441-50. Burd L, Severud R, Kerbeshian J, Klug MG.

Abortion and low birth weight are significantly associated with increased risk of autism in subsequent born children.

"Invited commentary: maternal effects in preterm birth--effects of maternal genotype, mitochondrial DNA, imprinting, or environment?" Little J. Am J Epidemiol. 2009 Dec 1;170(11):1386-7.

(ABSTRACT) Preterm birth is an important public health problem. A wide range of risk factors has been investigated, of which the strongest established is a woman's previous history of preterm birth. In this issue of the Journal, Boyd et al. (Am J Epidemiol. 2009;170(11):1358-1364) and Svensson et al. (Am J Epidemiol. 2009;170(11):1365-1372), using data on singleton livebirths from national birth registers linked with multigeneration databases, found evidence that maternal genetic factors impact on the risk for preterm birth, whereas paternal and probably fetal genetic factors do not. Possible caveats include missing information, the range of maternal risk factors included in the analyses, possible misclassification of these risk factors, and possible vertical transmission of microbial flora or behaviors from mother to daughter. Weinberg and Shi (Am J Epidemiol. 2009;170(11):1373-1381) build on the evidence regarding potential mechanisms underlying the heritability of preterm birth from these 2 and other studies, to evaluate the comparative ability of different study designs to distinguish among these potential mechanisms. These studies have different strengths, and a portfolio of studies of different designs and with more detailed phenotyping than previously done will be needed to probe further the etiology of preterm birth and thereby provide tools for its control.

(COMMENT) Little identifies "previous abortion" as a factor in pre-term birth, citing "Swingle HM, Colaizy TT, Zimmerman MB, et al. Abortion and the risk of subsequent preterm birth: a systematic review with meta-analyses. J Reprod Med. 2009;54(2):95–108."

"Induced termination of pregnancy and low birthweight and preterm birth: a systematic review and meta-analyses" Shah PS, Zao J. British J Ob Gyn 2009 Oct; 116(11):1425-1442.

Background History of induced termination of pregnancy (I-TOP) is suggested as a precursor for infant being born low birthweight (LBW), preterm (PT) or small for gestational age (SGA). Infection, mechanical trauma to the cervix leading to cervical incompetence and scarred tissue following curettage are suspected mechanisms.

Objective To systematically review the risk of an infant being born LBW/PT/SGA among women with history of I-TOP.

Selection criteria: Studies reporting birth outcomes to mothers with or without history of induced abortion were included from Medline, Embase, CINAHL and bibliographies of identified articles were searched for English language studies.

Data collection and analyses: Two reviewers independently collected data and assessed the quality of the studies for biases in sample selection, exposure assessment, confounder adjustment, analytical, outcome assessments and attrition. Meta-analyses were performed using random effect model and odds ratio (OR), weighted mean difference and 95% confidence interval (CI) were calculated.

Main results: Thirty-seven studies of low–moderate risk of bias were included. A history of one I-TOP was associated with increased unadjusted odds of LBW (OR 1.35, 95% CI 1.20–1.52) and PT (OR 1.36, 95% CI 1.24–1.50), but not SGA (OR 0.87, 95% CI 0.69–1.09). A history of more than one I-TOP was associated with LBW (OR 1.72, 95% CI 1.45–2.04) and PT (OR 1.93, 95% CI 1.28–2.71). Meta-analyses of adjusted risk estimates confirmed these findings.

Conclusions: A previous I-TOP is associated with a significantly increased risk of LBW and PT but not SGA. The risk increased as the number of I-TOP increased.

"Previous abortion and the risk of low birth weight and preterm births." Brown JS Jr, Adera T, Masho SW. J Epidemiol Community Health. 2008 Jan;62(1):16-22.

Abortions increase the risk of low birth weight by three fold and the risk of premature birth two fold. According to the authors, the effect is causal. "The accruing risk, says co-author Tilahun Adera at Virginia Commonwealth University, suggests that termination of pregnancy is a true cause of low birth weight and preterm birth rather than a variable associated with such conditions. 'It's not just an association,' he says. 'The risk of premature birth increases with the increasing number of abortions.'"[1]

OBJECTIVE: To investigate the association between previous abortion and low birth weight (LBW) and preterm birth (PB). METHOD: The study examined live, singleton births using data from the United States Collaborative Perinatal Project. Over 45,000 single-child live births from 1959 to 1966 were examined. Logistic regression was used to control for obstetric and medical history, and lifestyle and demographic factors. RESULT: Compared with women with no history of abortion, women who had one, two and three or more previous abortions were 2.8 (95% CI 2.48 to 3.07), 4.6 (95% CI 3.94 to 5.46) and 9.5 (95% CI 7.72 to 11.67) times more likely to have LBW, respectively. The risk for PB was also 1.7 (95% CI 1.52 to 1.83), 2.0 (95% CI 1.73 to 2.37) and 3.0 (95% CI 2.47 to 3.70) times higher for women with a history of one, two and three or more previous abortions, respectively. CONCLUSION: Previous abortion is a significant risk factor for LBW and PB, and the risk increases with the increasing number of previous abortions. Practitioners should consider previous abortion as a risk factor for LBW and PB.

"Cost consequences of induced abortion as an attributable risk for preterm birth and its impact on informed consent" Calhoun B, Shadigian E, Rooney B. Journal of Reproductive Medicine Oct. 2007

31.5% of preterm births are attributable to a history of induced abortion and that the initial neonatal hospital costs for treating preterm births until release from the hospital cost the nation over $1.2 billion per year. (With 1.2 million abortions per year, this translates to additional health care costs $1000 per abortion.) Moreover, this cost estimate does not include additional costs associated with follow-up care or with lifetime treatment costs associated with cerebral palsy (1096 cases per year) attributable to excess premature births attributable to abortion.

Particulate Matter Exposure and Preterm Birth: Estimates of U.S. Attributable Burden and Economic Costs. Trasande L, Malecha P, Attina TM. Environ Health Perspect. 2016 Mar 29.

Direct medical costs of preterm birth (PTB) and the costs of lost economic productivity (LEP) were calculated by the authors. The LEP was calculated based on a meta-analysis of PTB-associated IQ loss and data on relationships between IQ lost and LEP.

When all costs are calculated using 2010 dollars, for every 1% increased risk of PTB increases medical costs for the first five years of life due to PTB-associated developmental disability (Table 3) by $229 million. Similarly, every 1% increased risk of PTB increases lost economic productivity costs by $1074 million per year.

Per incidence of PTB, this factors into an estimated average cost of $48,077 in additional medical costs and $226,025 in lost economic productivity.

Projected on estimates attributing 31.5% of PTB to prior history of induced abortion, the total economic cost would be $41 billion per year . . . which if apportioned across 1.3 million abortions per year, would imply a hidden cost of $31,572 per abortion in economic costs associated with increased PTB alone.

"Infection and preterm birth", WW Andrews et al, Am J Perinatol 17 (7): 357, 2000

Preterm birth complicates 11% of all pregnancies in the U.S. and remains a leading cause of infant mortality and long-term neurological handicap. Despite widespread use of preventive strategies, the rate of preterm birth is increasing and the prevalence of long-term handicap to preterm birth is also increasing. Considerable data implicate a clinically silent upper genital tract infection as a key component of the pathophysiology of a majority of early spontaneous preterm births, but a minority of preterm births that occur near term.

"The role of infection in the etiology of preterm birth", M Toth et al, Obstet Gynecol 71(5):723, May 1988

A study at New York Hospital-Cornell University Medical College concluded that "collective evidence implicates preexisting infection of the uterine cavity as a predisposing factor in premature rupture of the membranes, preterm delivery, and amnionitis…. A strong correlation was found between preterm birth and a history of pelvic inflammatory disease… Amnionitis was also associated with a history of pelvic inflammatory disease."

The Epidemiology of Preterm Labor", JN Robinson et l, Seminars in Perinatology 25(4):204,2001

Factors associated with preterm labor and delivery include maternal conditions such as induced abortion. Maternal behaviors such as smoking and substance abuse can be risk factors for a short gestation.

"Impact of induced abortions on subsequent pregnancy outcome. The 1995 French national perinatal pregnancy survey, L Henriet, M Kaminski, Br J Obstet Gynaecol 108 :1036-1042 ,2001

In a national sample of 12,432 French women who had a singleton live birth during one week in 1995, there was a statistically significant increased risk of preterm birth of 30% for women with one prior abortion, and a 90% increased risk of preterm birth for women with two or more induced abortions compared to women with no induced abortion history.

"Abuse During Pregnancy: Effects on Maternal Complications and Birth Weight in Adult and Teenage Women," B. Parker et al., Obstet. Gynecol. 84: 323,1994

A study of poor African-American, Hispanic and white urban female residents from 1990- 1993 in Baltimore, Maryland and Houston, Texas found that physical and sexual abuse during pregnancy occured among one in five teens and one in six adult women. Abused women were significantly at risk for pregnancy complications as well as drug or alcohol use.

"Induced Abortion as a Risk Factor for Subsequent Fetal Loss," C Infante-Rivard and R Gauthier, Epidemiology 7:540, 1996.

In a Canadian case-control study of fetal losses and prior reproductive history in a Montreal obstetrical care facility during 1987-91, it was found that compared to women with no previous pregnancies (1.0), women with one prior pregnancy and no induced abortions had a non-significant (1.03) increased relative risk; women with two prior pregnancies and no induced abortions had a non-significant (0.71) reduced relative risk; women with one prior pregnancy and one prior induced abortion had a non-significant (1.41) increased relative risk; and women with two prior pregnancies and two prior abortions had a statistically significant (4.43) increased relative risk of fetal loss.)

"Induced Abortion and Subsequent Pregnancy Duration," W Zhou et al, Obstetrics and Gynecology 94:948, 1999.

A Danish study using national registries found a statistically significant 1.96 increased relative risk of preterm delivery for women with pregnancy intervals exceeding 12 months with one vacuum aspiration abortion, 2.62 increased relative risk for two vacuum aspiration abortions, and 2.16 for three vacuum aspiration abortions compared to women with other pregnancy outcomes and no induced abortion history.

"Risk factors associated with preterm and early preterm birth, univariate and multivariate analysis of 106,345 singleton births from the 1994 statewide perinatal survey of Bavaria," JA Martius et al, Eur J Obstet Gynecol Reprod Biol 80(2): 183-189, 1998.

In a mulitvariate analysis, an increased risk of early preterm birth was associated with previous induced abortion (OR 1.8, 1.57-2.13 ,95% CI)

"A Comparison of Risk Factors for Preterm Labor and Term Small for Gestational Age Birth," JM Lang et al, Epidemiology 7:369, 1996.

A study at the Boston Hospital for Women controlled for the effects of 23 factors on preterm labor and fetal growth retardation. Compared to women with no previous induced abortion (1.0) , women with one induced abortion had a non-significant (1.1) increased relative risk of preterm labor; women with two previous induced abortions had a statistically significant increased relative risk of (1.9); and women with three or more induced abortions had a statistically significant increased relative risk of (3.6).

"Very and moderate preterm births: are the risk factors different," ? Pierre-Yves Ancel et al, Br J Obstet Gynaecol 106: 1162-1170, 1999.

A case-control study in 15 European countries found that a previous first trimester abortion increased the risk of very preterm births (22-32 weeks) by 86% and increased the risk of moderate preterm births (33-36 weeks) by 58%. A previous second trimester abortion increased the risk of very preterm births by 267% and increased the risk of moderate preterm births by 133% compared to controls (37 weeks or more).

"The epidemiology of pre-term birth," Judith Lumley, Bailliere's Clinical Obstetrics and Gynaecology 7(3): 477, Sept. 1993

A study of more than 300,000 first singleton births in Victoria, Australia from 1986-1990 found that 6.5 per 1000 births were 20-27 gestational weeks where the woman had one prior induced abortion compared to 10.3 per 1000 births (two prior induced abortions) and 23.1 per 1000 births (three or more prior induced abortions). The rate of pre-term births at 32-36 gestational weeks was 54.1 per 1000 births where the women had one prior induced abortion, 78.7 per 1000 births where women had two prior induced abortions and 120.1 per 1000 births where women had three or more prior induced abortions. For purposes of analysis women who had experienced both induced and spontaneous abortions were excluded.

"Association of Induced Abortion with Subsequent Pregnancy Loss," A. Levin, S. Schoenbaum, R. Monson, P. Stubblefield, and K. Ryan Journal of American Medical Association243:2495(1980).

This study compared prior pregnancy histories of two groups of women, one having a pregnancy loss up to 28 weeks gestation and the other having a full-term delivery. Women who had two or more prior induced abortions had a twofold to threefold increase in first-trimester spontaneous abortions (miscarriage) between 14 to 20 and 20 to 27 weeks. The increased risk was present for women who had legal induced abortions since 1973. It was not explained by smoking status, history of prior spontaneous loss, prior abortion method, or degree of cervical dilation. No increased risk of pregnancy loss was detected among women with a single induced prior abortion.

"We compared prior pregnancy histories of two groups of multigravidas—240 women having a pregnancy loss up to 28 weeks' gestation and 1,072 women having a term delivery. Women who had had two or more prior induced abortions had a twofold to threefold increase in risk of first-trimester spontaneous abortion, loss between 14 to 19 and 20 to 27 weeks. The increased risk was present for women who had legal induced abortions since 1973. It was not explained by smoking status, history of prior spontaneous loss, prior abortion method, or degree of cervical dilatation. No increase in risk of pregnancy loss was detected among women with a single prior induced abortion. We conclude that multiple induced abortions do increase the risk of subsequent pregnancy losses up to 28 weeks' gestation."

"A Comparison of Risk Assessment Models for Term and Preterm Low Birthweight," R Michielutte et al, Preventive Medicine 21:98-109, 1992.

A large North Carolina study found that two or more previous induced abortions increased the risk of low birth weight in subsequent birth by 42%; one or more second trimester abortions increased the risk of low birth weight in subsequent birth weight by 78%; a previous live birth reduced the risk of low birth weight compared to no previous live birth.

"The association with multiple induced abortions with subsequent prematurity and spontaneous abortion," L.H. Roht, H. Aoyama, G.E. Leinen, Acta Obstet Gynaecol, Japan 23:140- 145,1976.

Induced abortion was associated with higher prematurity and spontaneous abortion rates in later pregnancies. Women who had 2 or more abortions had a 2-3 times increased risk of miscarrying a pregnancy.

"Late sequelae of induced abortion in primigravidae," 0. Koller and S.N. Eikhom, Acta Obstet. Gynecol. Scand, 56:311 (1977).

The total rates of later abortions and infants with low birth weight below 2500 grams was higher in women with a previous induced abortion than in women whose previous pregnancy ended in a spontaneous abortion or delivery.

"Influence of induced abortion on gestational duration in subsequent pregnancies," J.W. Vander Slikke and P.A. Treffers, British Medical Journal I, 270-272 (1978).

A Dutch study compared the outcome of subsequent pregnancies of 265 women who had at least one abortion in a previous pregnancy with the outcome in an age matched group of 265 with no abortion history. 6.4% women with abortion history had deliveries prior to the 32nd week of gestation compared to only 1.2% of the women with no abortion history.

"Late Sequelae of Induced Abortion: Complications and Outcome of Pregnancy and Labor," S. Harlap and M. Davies, AmJ. Epidemiology 102(3):217 (1975).

This study found that birthweight less than 2500 grams as well as a birthweight less than 2000 grams were significantly more frequent in an obstetric history of one or more induced abortions than in a group of patients without a history of induced abortion; 6.3% v. 4.7% below 2500 grams and 2.3% v. 1.4% below 2000 grams. The differences in birthweight were found to be due to preterm delivery and not to growth retardation. It was not clear whether the induced abortions in all cases immediately preceded the current pregnancy. Most abortions in this study were thought to have been illegal.

"Delayed reproductive complications after induced abortion," K. Dalaker, S.M. Lictenberg, G. Okland, Acta Obstel Gynecol Scand. 58:491-494,1979.

A Norwegian study compared 619 women who had their last pregnancy terminated by abortion to an age and parity matched group of women who continued the pregnancy to delivery. Among those who had not been pregnant previously the complications rate was 25.5% in the abortion group compared to 13.2% in the control which was statistically significant. Complications included first and second trimester abortion (miscarriage), cervical incompetence, pre-term delivery, ectopic pregnancy and sterility. After women had one or two live births there was no statistical significance between the two groups.

"Second-trimester abortion after vaginal termination of pregnancy," C.S.W. Wright, S. Campbell, J. Beazley, Lancet 1,1278-1279 (1972).

A British study compared the outcome of the subsequent pregnancy in 91 women who had induced abortions with a control group of 3233 women in which no induced abortions had occurred. In the group with prior induced abortion 9% had second trimester abortions (miscarriage) compared to only 0.9% in the group with no induced abortions.

"Gestation, Birth-Weight and Spontaneous Abortion in Pregnancy After Induced Abortion," Report of the Collaborative Study by World Health Organization Task Force on Sequelae of Abortion. The Lancet I, 142-145, January 20,1979.

In a study of 7228 European women from 8 cities the reduction in mean birth-weight associated with cigarette smoking varied from 120-146 grams. Low birth weight in the pregnancy after induced abortion by vacuum aspiration was 5.4% to 6.1% compared with 2.9%-4.7% for prior live birth or 3.7% if no previous pregnancy. Short gestation (258 days) was 4.7%-5.7% in the pregnancy after abortion with vacuum aspiration compared to 2.0%-3.9% for prior live birth or 2.4%-3.0% for no previous pregnancy. No significant differences between groups were found with respect to mid-trimester spontaneous abortions.

"Low Birth Weight in Relation to Multiple Induced Abortions," M.T. Mandelson, C.B. Maden. J.R. Daling, AmJ. Public Health 82(3):391-394, March, 1992.

In a Washington State study of 6541 white women who delivered their first child between 1984-87, 4.4% of women with no reported abortions had low birth weight babies (2500 grams or less) compared to 5.7% of women reporting 1 abortion, 7.7% of women reporting 2 abortions, 7.1% of women reporting 3 abortions, and 9.6% of women reporting 4 or more abortions. These differences approached statistical significance.

"Effects of legal termination on subsequent pregnancy," J.A. Richardson and G. Dixon, British Medical Journal 1,1303-1304 (1976).

This study observed more first-trimester abortions (miscarriages), second trimester abortions and premature deliveries (less than 37 week amenorrhea) in a group of 211 patients whose previous pregnancy was artificially interrupted than they observed in a parity matched group of 147 women whose previous pregnancy resulted in a spontaneous abortion. Ninety-one of the 211 women became pregnant again within 1 year despite good contraceptive advice.

"A study on the effects of induced abortion on subsequent pregnancy outcome," C. Madore, W.E. Haws, F. Many, A.C. Hexter, AmJ. Obstet. Gynecol 139:516-521,1981.

A California case-control study of 2081 women who had one or more induced abortions matched with 4098 controls without a history of abortion found that a prior induced abortion had a relative risk of 1.45 (1.06-1.99, 95% C.I.) of pregnancy failure (ectopic pregnancy, spontaneous abortion, fetal or neonatal death). Smokers had a relative risk of 1.85, (1.11-3.10, 95% C.I.) of pregnancy failure.

"Impact of Abortion on Subsequent Fecundity," Carol J. Hogue, Clinics in Obstetrics and Gynecology 13(1): 95, March, 1986

Comments of the author:

Compared to women who have previously delivered the risk of low birth weight is elevated for women delivering for the first time after an induced abortion by vacuum aspiration.

Studies of first-trimester spontaneous abortion following induced abortion have been seriously flawed.

Women who choose to have their first pregnancy terminated by abortion are at no increased risk of failing to conceive at a later date unless the abortion is complicated by infection leading to pelvic inflammatory disease. Women whose first pregnancy is terminated by vacuum aspiration are at no increased risk of subsequent ectopic pregnancy unless the abortion is complicated by pre-existing C. Trachomatis or post- abortion infection.

More research is needed before it is clear whether multiple induced abortions carry an increased risk of adverse pregnancy outcomes.

"Risks of Preterm Delivery and Small For Gestational Age Infants Following Abortion: A Population Study," R. Pickering and J. Forbes, British Journal of Obstetrics and Gynecology, 92:1106-1112, Nov. 1985.

Concludes that the relative risk of preterm delivery is significantly increased following abortion. "Late Sequelae of Induced Abortion: Complications and Outcome of Pregnancy and Labor," S. Harlap and A. Davies, American Journal of Epidemiology, 102(3):217- 224,1975. There was a significant increase in the frequency of low birth weight, compared to births in which the mother has no history of previous abortion.

"Pregnancy Complications Following Legally Induced Abortion," Erik Obel, Acta Obstet. Gynecol. Scand., 58: 485-490(1979).

The study could not demonstrate an increased frequency of low birth weight among women whose previous pregnancy had been terminated by legal abortion, but did find that the rate of deliveries before 37 weeks gestation increased with the number of induced abortions.

"Prospective Study of Spontaneous Fetal Losses After Induced Abortions," S Harlap, P. Shioho, S. Ramcharan, H. Berendes, and F. Pellegrin New England Journal of Medicine, 301(13):677-681, September 27,1979.

The relative risk of spontaneous fetal losses after induced abortion increased with the number of previous induced abortions and was not explained by the distribution of demographic and social variables.

"Habitual Abortion, Causes, Prevention and Management," William D. Schlaff, The Female Patient, 12:45-61 March, 1987.

A number of reproductive tract infections have been suggested as possible causes of recurrent [spontaneous] abortion. Unfortunately, there seems to be no clear causative association between most of these infections and reported miscarriages. It is often difficult to differentiate the effect of an infection on the fetus from the maternal effect. Furthermore, studies examining the impact of infections on fetal wastage are frequently confounded by the presence of many other variables. Habitual abortion has been noted in approximately 15 percent of patients with intrauterine synexhiae [Asherman's syndrome]. This syndrome may be produced by intrauterine infection, puerperal dilatation and curettage or abortion.

World Health Organization, Special Program of Research, Development and Research Training in Human Reproduction: Seventh Annual Report. (Geneva: WHO, November 1978).

A repeat abortion is associated with a two- to two and a half-fold increase in the rate of low birth weight and short gestation when compared with either one abortion or one live birth. Women were matched with women who had the same operative procedure. Cases and controls were matched also for age, smoking, institution and duration of gestation at entry into the study. See "Repeat Abortions Increase Risk of Miscarriage, Premature Birth and Low Birth-weight Babies" Family Planning Perspectives 11(1): 39- 40, Jan/Feb 1979

"Infection and preterm birth", WW Andrews et al, Am J Perinatol 17 (7): 357, 2000

Preterm birth complicates 11% of all pregnancies in the U.S. and remains a leading cause of infant mortality and long-term neurological handicap. Despite widespread use of preventive strategies, the rate of preterm birth is increasing and the prevalence of long-term handicap to preterm birth is also increasing. Considerable data implicate a clinically silent upper genital tract infection as a key component of the pathophysiology of a majority of early spontaneous preterm births, but a minority of preterm births that occur near term.

"The role of infection in the etiology of preterm birth", M Toth et al, Obstet Gynecol 71(5):723, May 1988

A study at New York Hospital-Cornell University Medical College concluded that "collective evidence implicates preexisting infection of the uterine cavity as a predisposing factor in premature rupture of the membranes, preterm delivery, and amnionitis…. A strong correlation was found between preterm birth and a history of pelvic inflammatory disease… Amnionitis was also associated with a history of pelvic inflammatory disease."

"The Epidemiology of Preterm Labor", JN Robinson et l, Seminars in Perinatology 25(4):204,2001

Factors associated with preterm labor and delivery include maternal conditions such as induced abortion. Maternal behaviors such as smoking and substance abuse can be risk factors for a short gestation.

"Impact of induced abortions on subsequent pregnancy outcome. The 1995 French national perinatal pregnancy survey, L Henriet, M Kaminski, Br J Obstet Gynaecol 108 :1036-1042 ,2001

In a national sample of 12,432 French women who had a singleton live birth during one week in 1995, there was a statistically significant increased risk of preterm birth of 30% for women with one prior abortion, and a 90% increased risk of preterm birth for women with two or more induced abortions compared to women with no induced abortion history.

Autism

Prenatal Environment and Perinatal Factors Associated with Autism Spectrum Disorder. J Ou, Y Shen, Y Li, G Xun, H Liu, Y He, H Guo, R Wu. Global Clinical and Translational Research 2019;1(3):100-108.

A history of induced abortion was associated with double the risk (OR = 2.07; 95% CI: 1.65-2.60) of a later child having autism.

Other Difficulties in Labor and Delivery

The Association between a History of Induced Abortion for Nonmedical Reasons and Maternal and Neonatal Perinatal Outcomes: A Retrospective Cohort Study, Siqi Zhang, Chunxia Lu, Qing Zhao, Ling ping Zhang et al. Preprint

Background: Following the implementation of the universal two-child policy in China, many multiparous women who had a history of induced abortion gave birth again. However, there is a lack of studies exploring the associations between induced abortion for nonmedical reasons and maternal and neonatal perinatal complications.

Methods: In this retrospective cohort study, the participants were multiparous women who gave birth to singleton babies at or after 28 weeks of gestation between December 1st, 2015, and December 1st, 2020. The exposure factor was maternal history of induced abortion for nonmedical reasons. Logistic regression models were used to adjust for potential confounding factors, and adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for maternal and neonatal perinatal outcomes. The dose‒effect relationships between the number of induced abortions for nonmedical reasons and adverse outcomes were tested by the Cochran‒Armitage trend test (p for trend). Stratified analyses were conducted to test the robustness of the results in subgroups with different maternal ages or interpregnancy intervals.

Results: There were 3,985 multiparous women with a history of induced abortion for nonmedical reasons and 1,823 multiparous women without such a history. Compared to women without such a history, women with a history of induced abortion for nonmedical reasons had increased risks of cesarean section (adjusted OR, 1.44; 95% CI: 1.23 - 1.69), placenta-related complications (adjusted OR, 2.14; 95% CI: 1.68 - 2.72), uterine-related complications (adjusted OR, 1.38; 95% CI: 1.05 - 1.81), HDP (adjusted OR, 1.49; 95% CI: 1.16 - 1.93), and preterm birth (adjusted OR, 1.24; 95% CI: 1.05 - 1.48) in subsequent pregnancy. In addition, there were dose-effect relationships between the number of induced abortions and the number of cesarean sections (P trend .001), placenta-related complications (P trend .001), uterine-related complications (P trend =.016), HDP (P trend =.0003), and preterm birth (P trend =.0006). Similar trends were observed in most subgroups with different maternal ages or interpregnancy intervals.

Conclusions: A history of induced abortion for nonmedical reasons was associated with increased risks of maternal and neonatal perinatal complications. Furthermore, dose‒effect relationships were observed for these associations.

Fear of childbirth after induced abortion in primiparous women: Population-based register study from Finland. Kemppainen V, Mentula M, Seppälä T, Gissler M, Rouhe H, Terhi S, Heikinheimo O, Niinimäki M. Acta Obstet Gynecol Scand. 2024 Feb;103(2):241-249. doi: 10.1111/aogs.14718. Epub 2023 Nov 20. PMID: 37984811; PMCID: PMC10823389.

• Introduction: Fear of childbirth (FOC) is a common obstetrical challenge that complicates about every 10th pregnancy. Background factors of FOC are diverse. We evaluated the association of induced abortion (IA) and FOC in subsequent pregnancy.
• Material and methods: Population-based register study based on three Finnish national registers: the Register of Induced Abortions, the Medical Birth Register and the Hospital Discharge Register. The study cases were primigravid women undergoing an IA in 2000-2015 and subsequent pregnancy ending in live singleton birth up to 2017. Each case had three controls, matched by age and residential area, whose first pregnancy ended in a live birth. The main outcome was the incidence of FOC in the subsequent pregnancy. In a secondary analysis, we assessed other risk factors for FOC.
• Results: The study cohort consisted of 21 455 women and 63 425 controls. Altogether, 4.2% of women had a diagnosis of FOC. The incidence was higher in women with a history of IA than in controls (5.6% vs 3.7%, P < 0.001). A history of IA was associated with higher odds for FOC: adjusted odds ratio [aOR] 1.20 with 95% confidence interval (CI) 1.11-1.30. In addition, a history of psychiatric diagnosis (aOR 3.48, 95% CI 3.15-3.83), high maternal age, 30-39 years old (aOR 1.55, 95% CI 1.43-1.67; P < 0.001) and ≥40 years old (aOR 3.00, 95% CI 2.37-3.77; P < 0.001) and smoking (aOR 1.20, 95% CI 1.11-1.31; P < 0.001) were associated with increased odds for FOC. Women living in densely populated or rural areas and those with lower socioeconomic class had lower odds for FOC.
• Conclusions: A history of IA is associated with increased odds for FOC in subsequent pregnancy. However, the associations of FOC with a history of psychiatric diagnosis and elevated maternal age (especially ≥40 years old) are more pronounced.
• Keywords: fear of childbirth, childbirth; induced abortion.

Previous pregnancy outcomes and subsequent pregnancy anxiety in a Quebec prospective cohort. Shapiro GD, Séguin JR, Muckle G, Monnier P, Fraser WD. J Psychosom Obstet Gynaecol. 2017 Jun;38(2):121-132. doi: 10.1080/0167482X.2016.1271979. Epub 2017 Jan 12.

INTRODUCTION: Pregnancy anxiety is an important psychosocial risk factor that may be more strongly associated with adverse birth outcomes than other measures of stress. Better understanding of the upstream predictors and causes of pregnancy anxiety could help to identify high-risk women for adverse maternal and infant outcomes. The objective of the present study was to measure the associations between five past pregnancy outcomes (live preterm birth (PTB), live term birth, miscarriage at <20 weeks, stillbirth at ≥20 weeks, and elective abortion) and pregnancy anxiety at three trimesters in a subsequent pregnancy.

METHODS: Analyses were conducted using data from the 3D Cohort Study, a Canadian birth cohort. Data on maternal demographic characteristics and pregnancy history for each known previous pregnancy were collected via interviewer-administered questionnaires at study entry. Pregnancy anxiety for the index study pregnancy was measured prospectively by self-administered questionnaire following three prenatal study visits.

RESULTS: Of 2366 participants in the 3D Study, 1505 had at least one previous pregnancy. In linear regression analyses with adjustment for confounding variables, prior live term birth was associated with lower pregnancy anxiety in all three trimesters, whereas prior miscarriage was significantly associated with higher pregnancy anxiety in the first trimester. Prior stillbirth was associated with greater pregnancy anxiety in the third trimester. Prior elective abortion was significantly associated with higher pregnancy anxiety scores in the first and second trimesters, with an association of similar magnitude observed in the third trimester.

DISCUSSION: Our findings suggest that the outcomes of previous pregnancies should be incorporated, along with demographic and psychosocial characteristics, into conceptual models framing pregnancy anxiety.

The association between previous single first trimester abortion and pregnancy outcome in nulliparous women. Hiersch L, Ashwal E, Aviram A, Rayman S, Wiznitzer A, Yogev Y. J Matern Fetal Neonatal Med. 2015 Jun 4:1-5.

Among women delivering a first born child, those with a history of induced abortion were at higher risk of induction of labor, cesarean section and retained placenta compared to those with no history of abortion.

Analysis of the high risk factor of birth defect in childhood from age 0 to 7 in Shandong province. WANG Lei-guang, QIU Yi. hinese Journal of Birth Health & Heredity. Feb. 2006.

A number of 183249 children aged 0-7 were surveyed randomly in Shandong of 9 model sides (county, city or district). A history of abortion is associated with 4.21 higher rate of birth defects.

Broken Maternity a Sisterhood of Sorrow Berkowitz K. International Journal of Childbirth Education V.24 No.3 September 2009.

• “If you have ever been pregnant before and that pregnancy ended in miscarriage, stillbirth, abortion or a dissatisfying birth experience, your experience of grief and loss may still be impacting your present pregnancy.”
• "To the extent that past traumas carry unrecognized or trapped emotional energy, they can profoundly impact our present and future experiences. They tend to make us believe and react as if what is happening to us now is just like what happened to us then, especially since traumatic experiences are characterized by events which cause loss, anger, fear and pain."
• “If a woman’s first pregnancy ends in abortion, she may associate later pregnancies with the agitation and buried psychic trauma of the first pregnancy. As a result, the births of later, wanted children can be times of anxiety and depression.“
• "Another woman described her pregnancy as “horrible”. She continues,”I kept feeling like something bad was going to happen to my baby. After the birth, I suffered major depression. I was in deep grief over my previous abortion. I didn’t understand it at the time, but it made it very hard to bond with my baby. I was a total failure at breastfeeding and comforting her. That was the most painful time in my life.""
• "In one survey by the Elliot Institute, nearly one half of the women surveyed stated that their negative feelings of their past abortion became worse when they gave birth to their children."

Severe Maternal Morbidity

Validation of an extended maternal comorbidity index (MCI) for prediction of severe maternal morbidity. Bruno, Ann M. American Journal of Obstetrics & Gynecology, Volume 230, Issue 1, S359

Objective

The expanded maternal comorbidity index (MCI) developed by Leonard et al uses pre-existing maternal health conditions (e.g., hypertension, asthma, etc.) to produce a risk score that predicts severe maternal morbidity (SMM). This tool has been adopted into clinical and research use without external validation in a data source not reliant on administrative codes. We assessed the validity of the MCI to predict SMM in a modern obstetric cohort with detailed medical record abstraction.

Study Design

Secondary analysis of a multicenter cohort of patients delivering on randomly selected days at 17 U.S. hospitals from 2019 through 2020. Data were manually abstracted from the medical record by trained staff. The MCI risk score was applied to all individuals within the cohort. The primary outcome was SMM as defined by the Centers for Disease Control and Prevention (CDC-SMM). Secondary outcomes included SMM without blood transfusion and the ACOG/SMFM definition of SMM (i.e., transfusion of ≥4 units of blood or intensive care unit admission). The median MCI score was calculated for the cohort, and the performance of the MCI risk score to predict SMM was assessed using the area under the receiver operating curve (AUC).

Results

Of 20,898 eligible patients, 668 (3.2%, 95% CI 3.0-3.4%) experienced CDC-SMM, 184 (0.9%, 95% CI 0.8-1.0%) experienced CDC-SMM without transfusion, and 142 (0.7%, 95% CI 0.6-0.8%) experienced ACOG/SMFM-SMM. In this cohort, the most common comorbidities were anemia (22.7%), maternal age at least 35 years (22.2%), and previous cesarean delivery (18.4%). The median MCI score in the cohort was 57.5 (IQR 47.5-71.5), which corresponded to a SMM risk of 7.9% (IQR 5.3-13.5%). The AUC for the MCI to predict CDC-SMM was 0.72 (95% CI 0.70-0.74; compared to AUC 0.78 in Leonard et al), CDC-SMM without transfusion was 0.83 (95% CI 0.79-0.86) and ACOG/SMFM-SMM was 0.79 (95% CI 0.75-0.83; Figure).

Conclusion

We externally validated the expanded MCI for prediction of SMM in a contemporary obstetric cohort. These findings support the ongoing use of this tool in research and clinical settings.

Note: There is evidence that a history of abortion may contribute to MCI and SSM An Expanded Obstetric Comorbidity Scoring System for Predicting Severe Maternal Morbidity. Leonard SA, Kennedy CJ, Carmichael SL, Lyell DJ, Main EK. Obstet Gynecol. 2020 Sep;136(3):440-449. doi: 10.1097/AOG.0000000000004022. PMID: 32769656; PMCID: PMC7523732.

Objective.

To develop and validate an expanded obstetric comorbidity score for predicting severe maternal morbidity (SMM) that can be applied consistently across contemporary U.S. patient discharge datasets.

Methods.

Discharge data from birth hospitalizations in California during 2016–2017 were used to develop the score. The outcomes were SMM, defined using the CDC index, and non-transfusion SMM (excluding cases where transfusion was the only indicator of SMM). We selected 27 potential patient-level risk factors for SMM, identified using ICD-10-CM diagnosis codes. We used a targeted causal inference approach integrated with machine learning to rank the risk factors based on adjusted risk ratios (aRR). We used these results to assign scores to each comorbidity, which sum to a single numeric score. We validated the score in California and national data sets and compared the performance to that of a previously developed obstetric comorbidity index.

Results.

Among 919,546 births, the rates of SMM and non-transfusion SMM were 168 and 74 per 10,000 births, respectively. The highest risk comorbidity was placenta accreta spectrum (aRR of 30.5 for SMM and 54.7 for non-transfusion SMM) and the lowest was gestational diabetes mellitus (aRR of 1.06 for SMM and 1.12 for non-transfusion SMM). Normalized scores based on the aRR were developed for each comorbidity, which ranged from 1–59 points for SMM and from 1–36 points for non-transfusion SMM. The overall performance of the expanded comorbidity scores was good (C-statistics were 0.78 for SMM and 0.84 for non-transfusion SMM in California data and 0.82 and 0.87, respectively, in national data) and improved upon prior comorbidity indexes developed for obstetric populations. Calibration plots showed good concordance between predicted and actual risks of the outcomes.

Conclusion.

We developed and validated an expanded obstetric comorbidity score to improve comparisons of SMM rates across patient populations with different comorbidity case mixes.

Bateman, et al Development of a Comorbidity Index for Use in Obstetric Patients. Obstetrics & Gynecology 122(5):p 957-965, November 2013. | DOI: 10.1097/AOG.0b013e3182a603bb

OBJECTIVE:

To develop and validate a maternal comorbidity index to predict severe maternal morbidity, defined as the occurrence of acute maternal end-organ injury, or mortality.

METHODS:

Data were derived from the Medicaid Analytic eXtract for the years 2000–2007. The primary outcome was defined as the occurrence of maternal end-organ injury or death during the delivery hospitalization through 30 days postpartum. The data set was randomly divided into a two-thirds development cohort and a one-third validation cohort. Using the development cohort, a logistic regression model predicting the primary outcome was created using a stepwise selection algorithm that included 24-candidate comorbid conditions and maternal age. Each of the conditions included in the final model was assigned a weight based on its beta coefficient, and these were used to calculate a maternal comorbidity index.

RESULTS:

The cohort included 854,823 completed pregnancies, of which 9,901 (1.2%) were complicated by the primary study outcome. The derived score included 20 maternal conditions and maternal age. For each point increase in the score, the odds ratio for the primary outcome was 1.37 (95% confidence interval [CI] 1.35–1.39). The c-statistic for this model was 0.657 (95% CI 0.647–0.666). The derived score performed significantly better than available comorbidity indices in predicting maternal morbidity and mortality.

CONCLUSION:

This new maternal comorbidity index provides a simple measure for summarizing the burden of maternal illness for use in the conduct of epidemiologic, health services, and comparative effectiveness research.

Neonatal Infection

"Reproductive history and the risk of neonatal sepsis," M. Germain, M.A. Krohn, J.R. Daling, Pediatric and Perinatal Epidemiology 9: 48-58,1995.

Induced abortion was associated with a statistically significant risk of neonatal sepsis in a subsequent pregnancy. The authors suggested that the procedures involved in induced abortion might produce a latent, sub-clinical infection until the next pregnancy, and then is transmitted to the newborn. Neonatal sepsis although it occurs in 1-10 cases per 1000 live births has a case fatality rate of 50-75% and is complicated by meningitis in 20-30% of cases and surviving children frequently have neurological defects.

Intraamniotic Infection

"Prior pregnancy outcome and the risk of intraamniotic infection in the following pregnancy," MA Krohn et al, Am J Obstet Gynecol 178: 381-385, 1998.

A Washington state study of hospital records found that the risk of intraamniotic infection was 4 times higher when the prior pregnancy outcome was an elective abortion compared to a prior birth of more than 20 weeks gestation.

Subsequent Fetal Malformation/Birth Defects

Prevalence of Congenital Heart Disease in Xinjiang Multi-Ethnic Region of China. Liu F Yang Y Xie X Li X Ma X et. al. PloS one 2015 vol: 10 (8) pp: e0133961

Chinese women with prior induced abortion multiply their risk of having newborn babies with congenital heart disease by over over five (5) times (5.47 odds ratio)

Preterm Birth and Poor Fetal Growth as Risk Factors of Attention-Deficit/ Hyperactivity Disorder. Sucksdorff M, Lehtonen L, Chudal R, Suominen A, Joelsson P, Gissler M, Sourander A. Pediatrics. 2015 Sep;136(3):e599-608.

ADHD and other disorders increase related to preterm birth

Maternal Reproductive History and the Risk of Congenital Heart Defects in Offspring: A Systematic Review and Meta-analysis. Feng Y, Wang S, Zhao L, Yu D, Hu L, Mo X. Pediatr Cardiol. 2015; 36(2):253-263. doi:10.1007/s00246-014-1079-z. Pediatr Cardiol. 2014:253-263. doi:10.1007/s00246-014-1079-z.

There is an increased risk of congenital heart defect (CHD) risk in offspring with a maternal history of prior pregnancies and abortions. CHD risk increased by 18 and 58% with a history of spontaneous abortion and induced abortion, respectively. There is a dose effect, with increased risk per exposure, with a 28% increased risk of CHD for each abortion to which a woman is exposed.

"A Population-Based Study of Gastroschisis: Demographic, Pregnancy, and Lifestyle Risk Factors," C P. Torfs et all.. Teratology 50: 44-53,1994

Urivariate analysis found a statistically significant risk of 1.96 of gastroschisis (an abdominal wall defect in newborns) where the mother had one or more elective abortions which was reduced to a 1.59 non-significant risk when adjusted for other reproductive variables.

"Hispanic Origin and Neural Tube Defects in Houston/Harris County. Texas, II Risk Factors." M.A. Canfield et al. Am. J. Epidemiology 143(1): 12,1996

In a study of Hispanic women, any previous pregnancy termination or fetal loss was significantly associated with anencephaly in subsequent births in a final logistic regression model, 2.48,1.20-5.10, CI 95%). In contrast, with one or more live births in comparison with no previous births, there was a slight non-significant decrease in risk. The authors stated that " one of the factors for increased risk for anecephaly among Hispanic women might be elective pregnancy termination")

"Induced abortion and subsequent congenital malformations in offspring of subsequent pregnancies," M.B. Bracken, T.R. Holford, Am.J. Epidemiology 109(4):425-432,1979.

A Connecticut case-control study during 1974-76 found that mothers with prior induced abortions had odds ratios above 1.0 with respect to the following specific congenital malformations of subsequently born children: Inquinal Hernia (OR 1.4, P=0.24); Anencephaly (OR 1.3, P=0.62); Poly-syndactyly (OR 2.7, P=0.02;); Downs (OR 1.5, P=0.46). Overall, white women delivering babies with congenital malformations were significantly less likely to report having had a previously induce abortion (OR 0.7, P=0.01) while black women who delivered were significantly more likely to have experienced a past induced abortion (OR 1.7, P=0.04).

"Late Sequelae of Induced Abortion: Complications and Outcome of Pregnancy and Labor," S. Harlap and A.M. Davies, Am J. Epidemiology 102(3): 217,1975.

A prospective study of 11,057 West Jerusalem mothers interviewed during pregnancy found that those who reported one or more prior induced abortions in the past were more likely to report bleeding in the 1st, 2nd. and 3rd. months of their pregnancy compared with women reporting no previously induced abortions. Women with prior abortions were less likely to have a normal delivery. In births following induced abortions, the relative risk of early neonatal death was doubled, while late neonatal deaths showed a 3 to 4 fold increase. Major and minor malformations were increased in the abortion group.

"Adverse effects on offspring of maternal alcohol abuse during pregnancy," Ouellette et al, New England Journal of Medicine 297:528-530,1977.

A 1974-75 study at Boston City Hospital found that infants born to heavy drinkers had more than twice the congenital abnormality (32%) compared to abstainers (9%) or light drinkers (14%).

"Cardiac remodelling as a result of pre-term birth: implications for future cardiovascular diseaseBensley JG, Stacy VK, De Matteo R, Harding R, Black MJ. Eur Heart J. 2010 Aug;31(16):2058-66. Epub 2010 May 7.

Premature delivery may impact heart development and increase vulnerability to cardiac disease.

"The Relationship Between Idiopathic Mental Retardation and Maternal Smoking During Pregnancy," C.D. Drew et. al. Pediatrics 97(4): 547, April, 1996.

A study by researchers at Emory University suggested that maternal smoking may be a preventable cause of mental retardation in children.

"Search for maternal factors associated with malformed human embryos: a prospective study," E. Matsunaga and K. Shiota, Teratology 21:323-331,1980.

3,474 malformed embryos from induced abortion were subjected to morphologic examination. 1.7% were malformed if there was no maternal genital bleeding; 4.9% were malformed with maternal genital bleeding; 15.8% were malformed if threatened abortion. Mothers of low parity showed an increased frequency of malformed embryos.

"Ectopic Pregnancy and Myoma Uteric: Teratogenic Effects and Maternal Characteristics," E. Matsunaga and K. Shiota, Teratology 21:61-69,1980.

In a Japanese study of 3614 well preserved human embryos derived from artificial termination of pregnancy, the frequency of malformed embryos recovered from ectopic pregnancies was 11.6% compared to 6.2% recovered from myomatous pregnancies and 3.3% from normally implanted pregnancies not complicated by myomas. Ed. Note: myoma means a benign neoplasm of the muscular tissue.