Cancer Risk Associated With Abortion

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Cancer Risks

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General Studies

"Depressed Mood And Development of Cancer," R.W. Linkins and G.W. Comstock,Am.J. Epidemiology 132(5): 962,1990.

A study was undertaken by researchers at Johns Hopkins University to determine whether premorbid depressed mood is associated with the development of cancer. Scores on the Center for Epidemiologic Studies Depression Scale were available for 2264 participants in a mental health study conducted in 1971-74 in Washington County, Maryland who were still free of cancer 2-4 years later. Over a 12 year follow-up period from 1975-87,169 cancers were diagnosed among these persons. Although there was only a slight association of depressed mood with subsequent cancer among the total study population, the association was much stronger among cigarette smokers. Compared with the risk seen in never smokers without depressed mood, those with a depressed mood at the highest level of smoking (25 or more cigarettes per day) had a 4.5 relative riskfor total cancer incidence, 2.9 for sites not associated with smoking (including breast cancer) and 18.5 for cancer at sites associated with smoking.

"Psychological Distress After Initial Treatment of Breast Cancer, Assessment of Potential Risk Factors," E. Maunsell, J. Brission, L. Deschenes, Cancer 70(1): 120, July 1,1992.

A Canadian study during 1984 among women with newly diagnosed breast cancer in Quebec City Hospital found that the number of stressful life events before diagnosis appeared to be strong indicators of the risk of psychological distress. High levels of psychological distress were present on 63% of the women with a history of depression compared to only 14.3% of those with no depression history.

Breast Cancer

While it is indisputable that studies have and continue to show a statistical association between abortion and breast cancer, the interpretation of these findings is highly controversial. The most up to date information regarding the abortion breask cancer link from the perspective of scientists who believe that women should be informed of this association is to be found at the Breast Cancer Prevention Institute
The American Cancer Society estimates that there will be 178,700 new invasive cases of breast cancer in women in 1998 and an estimated 43,500 women will die from breast cancer in 1998. One out of eight U.S. women will have breast cancer in their lifetime. The five year survival rate for U.S. white females is 86%. The five year survival rate for African-American females with breast cancer is 70%.

Protective Effect of "Early Childbirth"

Between 45-50% of U.S. women undergo induced abortion of their first pregnancy each year. It is well established that an early full-term childbirth has a protective effect against breast cancer in women. Breast feeding has also been demonstrated to have a modest protective effect against breast cancer. An increasing number of term births also protects against breast cancer. As the following studies indicate, all of these factors are independent protective factors against breast cancer

"Age at First Birth and Breast Cancer Risk," B MacMahon et al, Bulletin of the World Health Organization 43:209, 1970.

An international collaborative study of 250,000 women on breast cancer and reproductive experience was carried out in seven areas throughout the world. It was estimated that women having their first child under age 18 have only about one-third the breast cancer risk of those whose first birth is delayed until age 35 or more. The researchers also stated that " data suggested an increased risk associated with abortion contrary to the reduction in risk associated with full-term births."

"Age at Any Birth and Breast Cancer Risk," D Trichopoulos et al, Int'l J Cancer31:701, 1983.

Data gathered from an international-case control study of breast cancer and age at birth found that there was a 3.5% increase of risk for every one year increase of age at first birth. Age at subsequent births had an independent and smaller effect of a 0.9% increase of risk for every year increase of age at any birth.

"Effect of Family History , Body-Fat Distribution, and Reproductive Factors on the Risk of Postmenopausal Breast Cancer," TA Sellers et al, New England Journal of Medicine326:1323, 1992.

A 1986 survey of Iowa women found that the age-adjusted relative increased risk associated with late age at first pregnancy i.e. 30 years of age or more was 5.75( 3.15- 10.49, CI 95%) for women with a family history of breast cancer, and 2.04 (1.31-3.17, CI 95%) for women without such a family history.

"Exogenous Estrogens and Other Factors in the Epidemiology of Breast Cancer," JL Kelsey et al, Journal of the National Cancer Institute 67(2):327, 1981.

In a hospital-based case-control study of Connecticut women with newly diagnosed breast cancer in 1977-79, it was found that higher than average risks were found among women who had never given birth to a child, women with an early age at menarche, women who had given birth to their first child at a relatively late age, women with previous benign breast disease, and women with a history of breast cancer in a sister or mother.

"The Independent Associations of Parity, Age at First Full Term Pregnancy of Breast and Duration of Breast Feeding with the Risk of Breast Cancer," PM Layde et al, J Clin Epidemiol 42(10:963, 1989.

In a case-control study involving eight population-based cancer registries in the United States, it was found that the age at first full-term pregnancy exerted a strong influence on the risk of breast cancer. Parity and duration of breast feeding also had a strong influence on the risk of breast cancer.

"A Prospective Study of Reproductive Factors and Breast Cancer," I. Parity, G Kvale et al, Am J Epidemiology 126(5): 831, 1987.

A large prospective study of Norwegian women found a strong and highly significant inverse association between the number of full-term pregnancies and the risk of breast cancer . There were increasing protective effects among women with as high as fifteen children.

"A case-control study of parity, age at first full-term pregnancy, breast feeding and breast cancer in Taiwanese women," FM Lai et al, Proc Nat'l Sci Counc Repub China B:20(3):71, 1996.

A case-control study of Taiwanese women found that women having had more than three full-term pregnancies, were younger than age 30 at first full-term pregnancy, and breast feeding for more than 3 years, had significantly protective effects against breast cancer. The effect of the number of full-term pregnancies on the risk of breast cancer was independent of the age at first full-term pregnancy. Also, the effect of age at first full-term pregnancy and the number of full term pregnancies was also independent of the effect of breast feeding.

"Lactation and A Reduced Risk of Premenopausal Breast Cancer," PA Newcomb et al, New England Journal of Medicine 330:81, 1994.

Patients less than 75 years old identified from various statewide tumor registries were compared to controls who did not have breast cancer. It was found that premenopausal women who had lactated when compared with women who were parous but never lactated had a statistically significant reduced risk of breast cancer. However, there was no reduced risk in postmenopausal women who had lactated.

Canonical Variates in Post Abortion Syndrome, HP Vaughan, (Portsmouth NH: Institute for Pregnancy Loss, 1990)

In a study of 232 women seen at crisis pregnancy centers with self-reported post abortion syndrome an average of 11 years following their abortion, 67.5% had one or more children following their abortion, 9.6% had no children, and 22.8% had not tried to have children. Nineteen percent of the women had aborted their only pregnancy.

"Abortion and breast cancer risk in seven countries," K.B. Michels et. al.. Cancer Causes and Control 6: 75-82,1995

A study by researchers at the Harvard School of Public Health found that among parous women, those with a history of abortion exhibited a 29% increased risk if the incomplete pregnancy occurred before first birth (1.16-1.36, 95% CI) Spontaneous and induced abortions were grouped together.

Induced Abortion as an Independent Risk Factor For Breast Cancer

A meta-analysis of the association between induced abortion and breast cancer risk among Chinese females. Yubei Huang, et al. Cancer Causes & Control November 2013

Results: A total of 36 articles (two cohort studies and 34 case–control studies) covering 14 provinces in China were included in this review. Compared to people without any history of IA, an increased risk of breast cancer was observed among females who had at least one IA (OR = 1.44, 95 % CI 1.29–1.59, I 2 = 82.6 %, p < 0.001, n = 34). No significant publication bias was found among the included studies (Egger test, p = 0.176). The risk increased to 1.76 (95 % CI 1.39–2.22) and 1.89 (95 % CI 1.40–2.55) for people who had at least two IAs and at least three IAs, respectively. Subgroup analyses showed similar results to the primary results. Meta-regression analysis of the included studies found that the association between IA and breast cancer risk attenuated with increasing percent of IA in the control group (β = −0.022, p < 0.001).
Conclusion: IA is significantly associated with an increased risk of breast cancer among Chinese females, and the risk of breast cancer increases as the number of IA increases. If IA were to be confirmed as a risk factor for breast cancer, high rates of IA in China may contribute to increasing breast cancer rates.

Epidemiologic Studies: Induced Abortion and Breast Cancer Risk

This fact sheet identifies 73 studies (and counting) that examine abortion and breast cancer, listing the studies and their results.

Reproductive factors and breast cancer: A case-control study in tertiary care hospital of North India. Bhadoria A S, Kapil U, Sareen N, Singh P.Indian J Cancer 2013;50:316-21

History of abortion was also found to be positively associated with the risk of breast cancer with 6.26 times higher risk in women having a history of abortion. The history of abortions was found to be significantly higher in breast cancer cases as compared to controls, with the Relative Risk (RR) = 6.26 in women having a history of abortion.

Breast cancer and some epidemiological factors: A hospital based study. Jabeen S, et al.Journal of Dhaka Medical College 2013;22(1):61-66.

A twenty fold increased risk of breast cancer was associated with a history of abortion in this case-control study of Bengali women.

Meta-analysis of the Relationship between Abortion and Female Breast Cancer in China Zhou, et al. Bulletin of Chinese Cancer. 2007. 1:11-13.

[Purpose] To investigate the relationship between abortion and breast cancer in Chinese women. [Methods] The published case-control studies from 1989 to 2005 about correlation of abortion with breast cancer in China were analyzed using Meta-analysis method to assess the comprehensive relationship between abortion and female breast cancer. [Results] Based on the enrolled criteria, 6 articles was searched. The cumulative cases and controls were 1 440 and 1 785 respectively. Significant heterogeneity was detected among the 6 studies (Q=17.03, P0.05). OR of abortion (random effect model) was 2.04 (95% CI: 1.50~2.76). [Conclusions] This meta-analysis suggests a possible association between abortion and female breast cancer. Women with a history of abortion would have 2.04 times risk of being breast cancer than who without history of abortion.

Risk factors for triple-negative breast cancer in women under the age of 45 years." Dolle J, Daling J, White E, Brinton L, Doody D, et al. Cancer Epidemiol Biomarkers Prev 2009;18(4)1157-1166.

In a reversal of the NCI panel opinion that abortion was not linked breast cancer, this new study (including leading researchers who previously questioned the link) identifies abortion as a consistent risk factor, associated with a 40% increased risk of abortion. See Brind.

"Abortion and the Risk of Breast Cancer: A Case-Control Study in Greece," L. Lipworth et. al., Intl J. Cancer 61: 181-184,1995.

Using parous women with no history of abortion as the baseline, an induced abortion before a first full-term pregnancy was 2.06 times more likely to result in breast cancer compared with controls (1.45-2.90, CI 95%).

"Carcinoma of the breast associated with pregnancy," R.M. King et. al, Surg. Gynecol. Obstet. 160: 228-232,1985.

In a series of 63 pregnant patients at the Mayo Clinic, a 5-year survival of 43% was reported in the interrupted pregnancy group compared to 59% in the full-term pregnancy group. 86% of the 17 patients with Stage I disease who delivered survived.

"Breast Cancer and Pregnancy: the ultimate challenge," R.M. Clark, T. Chua, Clin. Oncology 1:11-18,1989.

Abortion during pregnancy may be deleterious to survival from breast cancer.

"Familial Risk of Breast Cancer and Abortion," N. Andrieu et. al.. Cancer Detection and Prevention, 18(1): 51-55,1994.

A French Study found that the risk of breast cancer associated with a family history of breast cancer increased with the number of abortions, induced as well as spontaneous, in a study of 495 breast cancer cases and 785 controls aged 20-56 years. For women who had undergone at least two abortions, the risk associated with a family history did not seem to depend on the type of abortion.

"Familial risk, abortion and their interactive effect on the risk of breast cancer-a combined analysis of six case-control studies," N. Andrieu et. al., Br. J. Cancer 72(3): 744-751, Sept., 1995.

Data obtained from France, Australia and Russia found that the relative risk conferred by a family history of breast cancer increased with the number of abortions (1.8 for no abortion, 1.9 for one abortion, and 2.8 for two or more. The familial risk was highest for those who had an abortion before first childbirth (1.9 for abortion after first childbirth and 2.7 for abortion before first childbirth).

"Breast Cancer Incidence and Mortality-United States, 1992," MMWR 45 (39): 833, October 4,1996.

In 1996, a total of 184,3000 new cases of and 44,300 deaths from invasive breast cancer are projected among women. In 1992, 43,063 U.S. women died from breast cancer. The death rate for white women was 26.0 per 100,000 women. The death rate for black women was 31.2 per 100,000 women.

"Induced abortion as an independent risk factor for breast cancer: a comprehensive review and meta-analysis," J. Brind et al, J. Epidemiology and Community Health 50: 481- 496,1996.

A meta-analysis of 28 published reports which included specific data on induced abortion and breast cancer incidence concluded that there was an independent risk of 30-50% for breast cancer as a result of induced abortion. Slightly higher risks for breast cancer among women with multiple abortions compared to one abortion were found in 7 of 10 studies. The authors stated that " a crucial distinction in the assessment of the real magnitude of breast cancer risk attributable specifically to induced abortion, is the ability to distinguish this from the known increased risk attributable to a delay in the first full term pregnancy by any means. From the point of view of women considering abortion, parous women would be subject only to the independent effect of induced abortion, whereas nulliparous women would be subject to both the risk enhancing effects of the abortion, depending on their age at time of abortion, and if and when they subsequently have any children."The authors also stated that " induced abortion may independently increase risk via the tumor promoting effect of considerably raised estradiol (estrogen) concentrations of early pregnancy, while denying a woman the differentiating effect of the hormonal milieu of late pregnancy. This differentiating effect is presumably the mechanism by which an early completed pregnancy confers permanent protection against breast cancer. In addition, induced abortion may enhance the estrogen mediated proliferation of normal but primitive cells, resulting in the presence of more cells which are vulnerable to subsequent primary carcinogenesis."

"Risk of Breast Cancer Among Young Women: Relationship to Induced Abortion," J. R. Daling et. al., J. of the National Cancer Institute 86(21): 1584, Nov. 2,1994.

Among women who had been pregnant at least once, the overall risk of breast cancer among women who had experienced an induced abortion was 50% higher which was statistically significant. Highest risks were noted when the abortions occurred among women younger than 18 years, particularly after 8 weeks gestation, or at 30 years or older.

"Reproductive and lifestyle risk factors for breast cancer in African-American Women," (Abstract) A.E. Laing et al , Genetic Epidemiology 11: 285-310,1994.

Data on lifestyle and reproductive variables were collected on 202 African-American women with breast cancer at Howard University Hospital and Washington Hospital Center between September 1989 and December, 1993. 70% of the cases had at least one unaffected sister to serve as a control. Conditional logistic regression analysis was conducted on 138 pairs of case-sister controls. Significant increases in risk for breast cancer were found to be conferred by experiencing induced abortions (OR= 2.44, p= 0.05).

"Exposure, susceptibility and breast cancer risk: A hypothesis regarding exogenous carcinogens, breast tissue development, the social gradients including black/white differences in breast cancer incidence," Nancy Kreiger, Breast Cancer Research and Treatment 13:205,1989.

It is well known that a second major round of breast tissue growth occurs during the first trimester of a woman's first pregnancy; that full development of this tissue into secretory cells requires a full-term pregnancy, that pregnancy promotes the vascularization of breast tissue, and that a woman's breast is qualitatively transformed by her first full-term pregnancy, resulting in a much higher ratio of differentiated to undifferentiated cells--If a woman's first pregnancy resulted in a first trimester abortion, the dramatic rise in undifferentiated cells that takes place during the first trimester would not be followed by the marked differentiation occurring during the second and third trimesters. The consequent sharp rise in the number of vulnerable cells would thus elevate the breast cancer risk.

"Her-2/neu and INT2 Proto-oncognene Amplification in Malignant Breast Tumors in Relation to Reproductive Factors and Exposure to Exogenous Hormones," H. Olsson, A. Borg, M. Ferno, J. Ranstam, H. Sigurdsson, J. National Cancer Inst. 83(20):1483, Oct. 16,1991.

In a study of genetic markers in premenopausal breast tumors, it was found that tumors from patients with any abortions before a first full-term pregnancy were 26 times more likely to show amplification for the INT2 gene which was an indication of faster tumor growth and lower survival.

"Breast Cancer and Pregnancy: The Ultimate Challenge," R.M. Clark, T. Chua, Clin Oncology A Journal Of The Royal College of Radiologists, 1:11-18 (1989).

In a Canadian study of 154 pregnant women with breast cancer, 20% of the 116 patients who carried their children to term were ultimately cured of their cancer, 40% of the 13 patients who spontaneously aborted were cured, but none of the 21 patients who had a "therapeutic" abortion survived. It was concluded that a "therapeutic" abortion did not confer any benefit and may reduce survival.

"Proliferation and DNA Ploidy in Malignant Breast Tumors in Relation to Early Oral Contraceptive Use and Early Abortions," H. Olsson, J. Ranstam, B. Baldetorp, S. Ewers, M. Ferno, D. Killander and H. Sigurdsson, Cancer 67:1285-1290(1991).

In a Swedish study at University Hospital, Lund, tumor tissue was analyzed indicating a higher rate of tumor cell proliferation for 175 premenopausal breast cancer patients. A history of early abortions was associated with a 49% higher S-phase fraction. A higher percentage of DNA aneuploid tumors was seen for patients with an early induced or spontaneous abortion (68% vs. 54%). Abortions (spontaneous or induced) before the first full-term pregnancy also were associated with a higher SPF compared with other young patients (under 20 years of age) with breast cancer (P=0.03).

"Rising Incidence of Breast Cancer Among Young Women in Washington," State/ E. White/ J.R. Daling, T.L. Norsted and J. Chu, Journal of the National Cancer Institute 79(2): 293-243, August 1987.

A study of 1/869 cases of breast cancer in Washington state women (ages 25-) found that the incidence of breast cancer increased 22% between 1974-77 and 1982-84. The estimated annual increase was 2.5%. The risk for black women doubled based on small numbers. Conclusion: One reason for the increase may be the dramatic exposure to induced abortion... Black women have a higher abortion rate than white women.

"Breast Cancer Risk Factors in African-American Women: The Howard University Tumor Registry Experience," A.E. Laing, F.M. Demenais/ R. Williams, V.W. Chen, G.E. Bonney,J. National Medical Association 85(12): 931-939, Dec. 1993.

In a Howard University case control study of African-American women seen at their hospital from 1978-1987, the multiple logistic estimates of the odds ratio for breast cancer among women under 40 years of age, between 41-49 years and over 50 years was 1.5, 2.8, and 4.7 respectively among women with a history of induced abortions compared to women with no history of induced abortions.

"The epidemiology of breast cancer as it relates to menarche, pregnancy, and menopause," M.C. Pike, B.E. Henderson and J.T. Casagrande in Hormones and Breast Cancer. M.C. Pike, P.K. Siiteri and C.W. Welsch, eds. (Cold Harbor N.Y.: Cold Harbor Pub. Co., 1981)

A means is proposed to explain the international variance in breast cancer. Early Menarche and the length of menstrual life prior to first pregnancy are particularly important risk factors. Three intervals of time are defined: menarche to first full-term pregnancy; first full-term pregnancy to menopause; and menopause to current age. The incidence of a given cancer at a particular time is a function of time. An equation was developed which can account for approximately 85% of the international variation in breast cancer. (Quoted from Diagnosis and Management of Breast Cancer, Marc E. Lippman, Alien Lichter and David Danforth (Philadelphia: W.B. Saunders Co., 1988)

"Age at First Birth and Breast Cancer Risk," B. MacMahon, P. Cole, T.M. Lin, C. Lowe, A. Mirra, B. Ravnihar, E. Salber, V. Valaoras and S. Yuasa, Bulletin of the World Health Organization 43: 209-221(1970).

An international collaborative study of breast cancer and reproductive experience was carried out in seven areas of the world. It was estimated that women having their first child under age 18 have only about one-third the breast cancer risk of those whose first birth is delayed until the age 35 or more.) (Data suggested an increased risk associated with abortion contrary to the reduction in risk associated with full-term births.)

"Susceptibility of the mammary gland to carcinogenesis II. Pregnancy interruption as a risk factor for tumor incidence," J. Russo and I.H. Russo, American Journal of Pathology100: 497 (1980)

Researchers studied pregnancy interruption as a risk factor in mammary tumor incidence in rats and found that pregnancy and lactation prior to chemically induced carcinogen administration protected the mammary gland from developing carcinomas and benign lesions. However, once pregnancy had been interrupted the protective effect was eliminated and animals were at the same risk as virgin animals treated with the carcinogen.

"Early Abortion and Breast Cancer Risk among Women under Age 40," H.L Howe, R.T. Senie, H. Bzduch and P. Herzfeld, International J. of Epidemiology 18(2):300-304 (1989).

Some 1/451 women with breast cancer were matched with population controls by year of birth and by residence using zip codes in upstate New York Those with a history of induced abortion as determined by fetal death records had a 1.9 odds ratio compared with controls.

"Oral Contraceptive Use and Early Abortion as Risk Factors for Breast cancer in Young Women," M.C. Pike, B.E. Henderson, J.T. Casagrande, I. Rosario and G. Gray, British Journal of Cancer 43: 72 (1981).

In a study of 163 white women less than 33 years of age in the Los Angeles area, a first- trimester abortion before a first full-term pregnancy was associated with a 2.4-fold increase in risk of breast cancer.

"Occurrence of Breast Cancer in Relation to Diet and Reproductive History: A Case-Control Study in Fukuoka, Japan," T. Hirohata, T. Shigematsu, A.M.Y. Nomura, National Cancer Institute Monograph 69:187,1985.

Two hundred and twelve female breast cancer patients among populations having low risk, intermediate risk and high risk were matched by sex and within 5 years of the same age with a hospital control of women who had no cancer and no benign breast disease as well as a neighborhood control randomly chosen from electoral listings. Among cases as compared to controls, a history of induced abortion had a 1.19 relative risk, which increased to 1.52 after adjustment by multiple logistic regression. Natural or spontaneous abortion had a 1.53 unadjusted relative risk ,which increased to 1.91 once adjusted by multiple logistic regression.

"Breast Cancer in Premenopausal and Postmenopausal Women," K. Stavraky and S. Emmons, Journal National Cancer Institute 53(3):647, Sept., 1974.

In a case-control study of premenopausal and postmenopausal women with breast cancer admitted to the Ontario Cancer Foundation, London, Canada during 1967-71 were compared to women admitted to the same clinic during the same period with benign and malignant sites other than breast. Compared with control patients, postmenopausal breast cancer patients had an excess of women who had at least one abortion (37% v. 27%).

"Risk of breast cancer in relation to reproductive factors in Denmark," M Ewertz and S.W. Duffy, British J. Cancer 58:99,1988.

All Danish women less than 70 years of age diagnosed with breast cancer in 1983-84 identified from the files of the Danish Breast Cancer Cooperative and the Danish Cancer registry , were compared with an age stratified sample of women drawn from the general population. Women whose first pregnancy was terminated by spontaneous or induced abortion before 28 weeks gestation had a 1.43 relative risk (1.10-1.84, 95% C.I.) of breast cancer compared to women whose first pregnancy was carried to term. Never pregnant women had a 1.47 relative risk (1.14-1.90, 95% C.I.) compared to women whose first pregnancy was carried to term.
Based upon small numbers, women with no full term pregnancies and one induced abortion had a 3.86 relative risk (1.08-13.6, 95% C.I.) for breast cancer compared with nulliparous women who had no abortion history. Again, based upon small numbers women who had no full term pregnancies and one first trimester spontaneous abortion had a 2.63 relative risk (0.83-8.32, 95% C.I.) compared to nulliparous women who had no abortion history. It was concluded that pregnancies have to be carried to term to offer the protective effect against breast cancer.

"Induced Abortion And Risk For Breast Cancer: Observed Relationship In Benin City, Nigeria" MI Momoh, AN Olu-Eddo. Sahel Medical Journal Vol. 11 (4) 2008: pp. 131-133

Patients and Methods: Biodata, risk factors, parity and abortion profile of all 145 female breast cancer patients seen in over a three year period were entered into a data sheet and analyzed by simple proportions and percentages.
Results: Breast cancer patients who had procured induced abortion were diagnosed with the disease nearly a decade and half earlier than in breast cancer patients who never had induced abortion.
Conclusion: Induced abortion, in the presence of same risk factors for breast cancer, caused the disease to be induced at a much earlier age than in the patients who did not procure abortion. We, therefore, advocate that induced abortion be discouraged. Women who must have an abortion should be counseled on increased risk of breast cancer as part of the informed consent for termination of pregnancy.

"Women in China See 17% Higher Breast Cancer Risk From Abortion

Xing P, Li J, Jin F. A case-control study of reproductive factors associated with subtypes of breast cancer in Northeast China.” Humana Press, e-publication online September 2009.

"Breast cancer risk factors in Turkish women - a university hospital-based nested case control study. Ozmen et al. World J Surg Onc 2009;7:37.]

A new study done on women in Turkey who had abortions had a 66 percent increased risk of contracting breast cancer. Women having a spontaneuous abortion, or miscarriage were not at an elevated risk.
BACKGROUND: Breast cancer has been increased in developing countries, but there are limited data for breast cancer risk factors in these countries. To clarify the risk for breast cancer among the Turkish women, an university hospital based nested case-control study was conducted.
METHODS: Between January 2000 and December 2006, a survey was prospectively conducted among women admitted to clinics of Istanbul Medical Faculty for examination and/or treatment by using a questionnaire. Therefore, characteristics of patients diagnosed with breast cancer (n = 1492) were compared with control cases (n = 2167) admitted to hospital for non-neoplastic, non-hormone related diseases.
RESULTS: Breast cancer risk was found to be increased in women with age (> or = 50) [95% confidence interval (CI) 2.42-3.18], induced abortion (95% CI 1.13-1.53), age at first birth (> or = 35) (95% CI 1.62-5.77), body mass index (BMI > or = 25) (95% CI 1.27-1.68), and a positive family history (95% CI 1.11-1.92). However, decreased breast cancer risk was associated with the duration of education (> or = 13 years) (95% CI 0.62-0.81), presence of spontaneous abortion (95% CI 0.60-0.85), smoking (95% CI 0.61-0.85), breast feeding (95% CI 0.11-0.27), nulliparity (95% CI 0.92-0.98), hormone replacement therapy (HRT) (95% CI 0.26-0.47), and oral contraceptive use (95% CI 0.50-0.69). On multivariable logistic regression analysis, age (> or = 50) years (OR 2.61, 95% CI 2.20-3.11), induced abortion (OR 1.66, 95% CI 1.38-1.99), and oral contraceptive use (OR 0.60, 95% CI 0.48-0.74) were found to be associated with breast cancer risk as statistically significant independent factors.
CONCLUSION: These findings suggest that age and induced abortion were found to be significantly associated with increased breast cancer risk whereas oral contraceptive use was observed to be associated with decreased breast cancer risk among Turkish women in Istanbul.

Cervical Cancer

Human papillomavirus infection (HPV) has been identified as the cause of cervical cancer. A contributing factor for cervical cancer is smoking. It is known that postabortion women will smoke more cigarettes than women with other reproductive outcomes. Thus, induced abortion may have an indirect role in the development of cervical cancer.

Determinants of cervical human papillomavirus infection:differences between high and low onocogenic risk types, PK Chang et al, J Infect Dis 185(1):28, 2002.

A survey of Hong Kong women who participated in cervical cancer screening found that the overall prevalence of HPV was 7.3%. Previous induced abortion was an 87% statistically significant increased risk for HPV for women at high risk for HPV, a 51% statistically significant increased risk for women with any HPV, and a 97% statistically significant increased risk for women with unknown risk for HPV. Other risk factors for HPV included lifetime number of sexual partners, smoking, and having smokers in the family.

"Induced Abortion in Taiwan," P.D. Dong, R.S. Lin, J. Royal Soc. Health 100-108, April, 1995

In a study of 17,047 women in Taipei, Taiwan who attended family planning services centers in 1991-1992 55% of the women had a normal Pap smear, 44% had an atypical finding and only 0.9% had dysplasia. A significantly positive trend was found between those women having had increasing numbers of induced abortions and the incidence of cervical dysplasia (P<0.01)

"Papillomavirus Infection Among Abortion Applicants and Patients at a Sexually Transmitted Disease Clinic," P.A. Csango et. al.. Sexually Transmitted Diseases 19(3): 149, May/June 1992.

A Norwegian study found that 6.1% of induced abortion applicants had human papillomavirus (HPV) infection. The proportion of high-risk HPV was 89.7%. HPV appears to be a risk factor for cervical cancer.

"Induced abortion as cancer risk factor: a review of epidemiological evidence," Larissa I. Remennick, J. Epidemiol Community Health 44(4): 259-264, Dec. 1990.

This article reviewed several studies on women in the Soviet Union and surrounding areas. It was reported that the majority of cervical cancers in Armenia were registered in three cities where induced abortion rates have been high. Where induced abortion rates have been lower in other regions, cervical cancer incidence has also been lower. Similarly, induced abortion and cervical cancer is high in migrant women, while cervical cancer and induced abortion is low in indigenous women. The author suggested that mechanisms of induced abortion influence on cervical carcinogenessis may be multiple. The first mode of action may be via general endocrine stress in the reproductive system resulting from termination of pregnancy related processes. Another is through mechanical trauma and possible infection associated with the dilation and curettage or incomplete evacuation of the embryo and placenta. Chronic inflammatory lesions may arise in cervical tissue on the site of this trauma, as well as cell abnormalities. In the course of time, the latter may undergo malignant transformation and/or facilitate the action of exogenous carcinogenic agents.

"Human Papillomaviris Infection and Other Risk Factors For Cervical Neoplasia: A Case-Control Study," E.A. Morrison, G. Ho, S.H. Vermund, G.L. Goldberg, A.S. Kadish, Int'l Journal of Cancer 49:6-13,1991.

A case-control study of inner city women in a Bronx, New York hospital during 1986-88 found that infection with human papillomaviris (HPV) was the major risk factor for cervical squamous intraepithelial lesions.

"Cigarette Smoking and Dysphasia and Carcinoma In Situ of the Uterine Cervix," E. Trevathan, P. Layde, L.A. Webster, J.B. Adams, J. American Medical Association 250(4): 499, July 22-29,1983.

A case-control study among black women in Atlanta, Georgia aged 17-55 from 1980-81 compared women attending a dysphasia clinic with those attending a family planning clinic at the same hospital who had at least two normal pap smears. Cigarette smoking was significantly associated with carcinoma in situ, severe dysphasia, and mild-moderate dysphasia (relative risks, 3.6, 3.3 and 2.4 respectively). Cumulative exposure to cigarette smoking, as measured by pack-years smoked was strongly related to the risk of these conditions. Women with 12 or more pack-years of exposure had relative risks of 12.7,10.2 and 4.3 respectively, for the three conditions. Ed. Note: Women with induced abortions are known to have higher smoking rates than women with other pregnancy outcomes.

"Editorial Commentary: Smoking and Cervical Cancer-Current Status," L.A. Brinton, Am. J. Epidemiology 131(6): 958,1990.

Smoking may act as a late stage carcinogen. Given the well- recognized continuum of disease from dysplasia to carcinoma in situ to invasive cancer. Further investigations are needed to address the effects of smoking on the natural history of cervical neoplasia.

"Effect of Cigarette Smoking on Cervical Epithelial Immunity: A mechanism for Neoplastic Change?," S.E. Barton, D. Jenkins, J. Cuzick, The Lancet, September 17,1988, p. 652-654.

Cigarette smoking was associated with a significant and dose-dependent decrease in the concentration of Langerhans' cells, the most prominent type of antigen-presenting cell in normal cervical epithelium. This reduction in the number Langerhans' cells available to detect and present viral antigens to T lymphocytes may facilitate the establishment and persistence of local viral infection. This could increase the likelihood of a virally induced neoplastic transformation, as has been proposed for HPV. These findings of a local immunological effect of smoking on cervical epithelium may explain the means by which cigarette smoking contribute to the development of cervical neoplasia. Citing "The wart virus and genital neoplasia: a casual or causal association." A. Singer, D.J. McCance, Br.J. Obstet. Gynaecol. 92:1083,1986.

"HPV co-factors related to the development of cervical cancer: results from a population-based study in Costa Rica," A Hildesheim et al, Br J Cancer 84(9):1219-1216, May, 2001.

Women who smoked 6 or more cigarettes per day had a 2.7 increase in relative risk for human papillomaviris or cervical cancer compared to non-smokers.

"Smoking, diet, pregnancy and oral contraceptive use as risk factors for cervical intra-epithelial neoplasia in relation to human papillomavirus infection," L Kjellberg et al, Br J. Cancer 82(7):1332-1338, April, 2000.

After taking HPV into account, smoking appeared to be the most significant environmental factor for cervical neoplasia.

"Reproductive patterns and cancer incidence in women: a population-based correlation study in the USSR," L.I Remennick, Int'l. J. Epidemiology 18: 498, 1989.

A correlation study in the USSR based on official abortion statistics and regional cancer incidence data for the period 1959-1985 showed a significant contribution of induced abortion to the variance of cervical cancer. The correlation between cervical cancer age adjusted incidence rates for women in 70 areas of Russia was 0.77 according to parametric tests and also 0.77 according to Spearman non-parametric rank criteria.

"Oral Contraceptive Use and Breast or Cervical Cancer: Preliminary Results of A French Case-Control Study," M.G. Le, A Bachelot, F. Doyon, A. Kramar, C. Hill in Hormones and Sexual Factors in Human Cancer Aetiology, Eds. J.P. Wolff, J.S. Scott, (New York: Excerpta Medica, 1984) 139-147.

A French case-control study during 1982-84 in 8 hospital centers in France of women age 45 or less with histologically verified cervical cancer compared cases with two control subjects with respect to the hospital center, date of interview (within 4 months) and age (within 2 years). Eighty-four cases of cervical cancer were compared with 83 control subjects with nonmaligant diseases and 43 control subjects with nongynecological cancer using logistic miltifactoral regression methods. The relative risk for women with cervical cancer and one abortion was 2.3 (P-value 0.001) compared to women with no abortion. The relative risk for cervical cancer for women with 2 or more abortions compared to women with no abortion was 4.92 (P-value 0.001). The study did not state whether the abortions were spontaneous or induced.

"Oral Contraceptives and Cervical Carcinoma in Situ in Chile," R. Molina, D.B. Thomas, A. Dabancens, Cancer Research 48:1011-1015, Feb. 15,1988.

A case-control study of cervical carcinoma in situ was conducted by a standard questionnaire among 133 women aged 15-50 years between 1979-85 in Santiego, Chile. The 254 controls were 2 women in the same 5 year age group as the corresponding case and who also had a normal Pap smear closest in time to the abnormal smear that led to the carcinoma in situ diagnosis. Several sexual variables were associated with an increased risk of carcinoma in situ. These included history of prior miscarriages, any prior aborted pregnancy, including spontaneous and induced abortions, total number of pregnancies, number of sexual partners and age at first sexual intercourse, The relative risk for carcinoma in situ for women with a history of any abortion (spontaneous or induced) compared to women with no abortion history was 1.85 (1.20-2.86, 95% C.I.). The relative risk for carcinoma in situ for a woman with an induced abortion was 1.38 (0.84-2.27, 95% C.I.) compared to women with no induced abortion history.

"Risk factors for adenocarcinoma of the cervix: A case-control study," F. Parazzini, C. LaVecchia, E. Negri, M. Fasoli, G. Cecchetti, Br. J. Cancer 57:201,1988.

A case-control study of 39 cases of cervical adenocarcinoma were compared to 409 controls admitted to area hospitals in the Milan, Italy area during 1981-86 for surgical or other traumatic injury. The median age for both cases and controls was 53 years. A history of one or more induced abortions has a relative risk of 2.5 (1.2-5.3, 95% C.I.) for cervical adenocarcinoma compared to women with no induced abortion history using Mantel-Haenszel estimates adjusted for age and age at first birth and parity. The Mantel- Haenszel estimates of relative risk adjusted for age at first intercourse were 3.7 (1.6-8.2, 95% C.I.) for a woman with a history of one or more induced abortions compared to a woman with no history of induced abortion.

"Reproductive factors and the risk of invasive and intraepithelial cervical neoplasia," F. Parazzini, C. LaVecchia, E. Negri, G. Ceccheti, L. Fedele, Br. J. Cancer 59:805-809, 1989.

A case-control study by researchers in Milan Italy of 528 cases of invasive cancer was compared with 456 control subjects hospitalized for acute conditions unrelated to any of the established or suspected risk factors for cervical cancer. Relative risks for invasive cervical cancer for women with one induced abortion compared to women with no induced abortion history were 1.89,1.60 and 1.69 based upon Mantel-Haenszel (M-H) estimates adjusted for age, M-H estimates adjusted for age and age at first intercourse, respectively. For women with a history of two or more induced abortions compared with women with no induced abortion history the M-H estimates of risk were 2.38, 2.41 and 1.44 based upon the same adjustments in the same order as above.
When relative risks for induced abortion were subjected to multiple logistic regression equations including adjustments for age, marital status education, age at first intercourse, number of sexual partners, history of Pap smears, smoking habits, oral contraceptive use number of live births, and age at first birth, the relative risk computed by multiple logistic regression ranged from 1.26-1.39 for women with one or more induced abortions compared to women reporting no induced abortion with no significant trend shown with increasing number of induced abortions.

"Epidemiological Study of Carcinoma in Situ of the Cervix," I. Fujimoto, H. Nemoto, K. Kuduka, The Journal of Reproductive Medicine 30(7): 535, July 1985.

During 1950-79, 1248 women with carcinoma in situ of the cervix were treated in the Department of Gynecology at the Cancer Institute Hospital in Tokyo, Japan. Cases were compared with noncancer controls admitted to the outpatient clinic of the same hospital at the same time. 69.4% of the cases vs. 55.9% of the controls reported an abortion ,which was statistically significant. The rate of repeated abortions was higher in the cases than the controls with seven the highest number among the cases.

"Characteristics of Women with Dysplasia or Carcinoma in Situ of the Cervix Uteri," R.W.C. Harris, L.A. Brinton, R.H. Cowdel, D. Skegg, Br. J. Cancer 42:359, 1980.

A British case-control study compared women with abnormal cervical smears with a control group. Women were classified as having severe dysplasia, mild dysplasia, carcinoma in situ or normal histology. Women with mild dysplasia, severe dysplasia and carcinoma in situ were more likely to report having had a pregnancy terminated but it was statistically significant for mild dysplasia only. (22.7% v. 6.2%) Relative risk 2.76 (1.1-6.8, 95% C.I.)

"Marital and Coital Factors in Cervical Cancer," C.E. Martin, Am. J. Public Health57(5): 803, May, 1967.

A retrospective study of 40 Jewish women in the New York City area during 1960-63 and diagnosed as having invasive or in situ squamous cell carcinoma were compared to 36 Jewish women with a recent hysterectomy and known to be free from uterine cancer. 42.5% of cases vs. 16.7% of controls reported an induced abortion which was statistically significant. Other significant factors for cervical cancer included two or more coital partners, first coitus before age 20, extramarital affairs, coitus with a non-Jew.

"Epidemiology of Cancers of the Uterine Cervix and Corpus, Breast and Ovary in Israel and New York City," H.L. Stewart, L.J. Dunham, J. Casper, J. of the National Cancer Institute 37(1); 1-96,1966.

In a case-control study of New York City and Israeli women, the age at first intercourse and age at termination of pregnancy were found to be strongly related to each other. The median ages of termination of first and last pregnancy were consistently lower for patients with cancer of the cervix than for control patients in each ethnic group, p.35.)

===Aborted Women: Silent No More, David C. Reardon, ( Chicago: Loyola Press, 1987).

This work includes personal testimonies from two women describing cervical cancer following induced abortion. In the sample of 252 women surveyed approximately 10 years following their abortion, 4% reported cervical cancer which they attributed to their induced abortion.

"Epidemiologic Study of Carcinoma in Situ of the Cervix," I. Fujimoto, H. Nemoto, K. Fuduka, S. Masubuchi, J. of Reproductive Medicine 30(7): 535, July 1985.

In a study of 1,248 cases of carcinoma in situ of the cervix in Tokyo, the women in the cancer group had a significantly greater number of abortions than the control group. It was concluded that the cervical repair process after abortion seems to be too important to disregard as a factor in the development of carcinoma in situ.

"Pap Screening for Teenagers: A life-saving Precaution," Mark Spitzer and Burton A. Krumholz, Contemporary OB/GYN 31(1):3341, January 1988;

Dysplasia of the cervix is increasing among adolescents. Sexually active teenagers, especially those who become pregnant, are at high risk for developing cervical dysplasia and, ultimately, cervical cancer.

"Abnormal Cervical Cytology in Sexually Active Adolescents," Joseph F. Russo and Damell Jones, Journal of Adolescent Health Care 5: 269-271(1984).

Pap smears on 1,207 sexually active adolescents in a public health department of eastern North Carolina turned up 11% with abnormal findings. Seventy-two percent of those women evaluated by colposcopy with directed biopsies had cervical intraepithelial neoplasia.

Ovarian Cancer

"Incomplete Pregnancies and Ovarian Cancer Risk," E. Negri et. al., Gynecologic Oncology 47: 234-238,1992.

An Italian case-control study found an inverse relationship between the total number of incomplete pregnancies and ovarian cancer risk which was 0.7 for one voluntary abortion and 0.8 for two or more voluntary abortions.

"Determinants of Ovarian Cancer Risk I. Reproductive Experiences and Family," History, D. Cramer, G. Hutchinson, W. Welch, R. Scully and K. Ryan, Journal of the National Cancer Institute 71(4): 711-716, October 1983.

In a study of 215 white females in the greater Boston area during 1978-81, pregnancy exerted a strong protective effect against ovarian cancer, which increased with the number of live-born children.

"An Epidemiologic Study of the Relationship of Reproductive Experience to Cancer of the Ovary," D.J. Joly, A. Lillenfeld, E. Diamond and I. Bross, American Journal of Epidemiology99(3): 190-209 (1974).

Ovarian cancer cases had a larger proportion of women who had never been pregnant or had no more than two pregnancies, as compared with controls. The relative risk of ovarian cancer increases as the number of pregnancies decreases.

"The Woman at Risk for Developing Ovarian Cancer," L. McGowan, L. Parent, W. Lednar and H. Morris, Gynecologic Oncology 7: 325-344 (1979).

In a case-control study of women in the Washington D.C. area during 1974-77, nulligravidas were 2.45 times more likely to develop malignant ovarian tumors and 2.9 times more likely to develop carcinomas of low malignant potential than women who were pregnant three or more times. The risk of ovarian cancer was greatly reduced among women who had at least one pregnancy. Women with ovarian cancer did not have more spontaneous abortions, still births or defective children than their controls.

""Incessant Ovulation" and Ovarian Cancer," J.T. Casgrande, M.C. Pike, R.K. Ross, E.W. Louie, S. Royard and B.E. Henderson, The Lancet, July 28,1979, pp. 170-173

The risk of ovarian cancer is clearly decreased directly by factors that suppress ovulation.

"Events of Reproductive Life and the Incidence of Epithelial Ovarian Cancer," H. Risch, N. Weiss, J.L. Lyon, J. Daling and J. Liff, American Journal of Epidemiology 117(2): 128- 139 (1983).

Women with ovarian cancer reported fewer full-term pregnancies, fewer miscarriages and less total time breastfeeding than controls.

"Does Pregnancy Protect Against Ovarian Cancer?," V. Beral, P. Fraser and C. Chilvers, The Lancet, May 20,1978, pp. 1083-1087.

A study by English epidemiologists found that there was a clear inverse relationship between completed family size and the death of women from ovarian cancer among women in England and Wales. They reported that, " the findings suggest that pregnancy- or some component of the childbearing process-protects directly against ovarian cancer. This protection seems to persist throughout life." The authors of the study stated that, "ovarian cancer is rare in populations that do not practice birth control. How pregnancy protects against ovarian cancer is unclear. If suppression of ovulation is the key factor, then breast-feeding, which suppresses ovulation, should reduce the risk of ovarian cancer. A pregnancy of short gestation, i.e., one that ended as an abortion, should confer less protection against ovarian cancer than a full-term pregnancy."

"Risk factors for ovarian cancer-a case control study," M Booth et al, Br J Cancer 60:592, 1989 (During 1978-1983, a hospital-based study of 235 British women with histologically diagnosed epithelial ovarian cancer was compared to 451 women hospitalized for other reasons. Childbirth was found to be more protective against epithelial ovarian cancer than incomplete pregnancies.)

"Incomplete pregnancies and risk of ovarian cancer, Washington, United States," M-T Chen et al, Cancer Causes and Control 7:415, 1996.

In a study of 322 white female residents aged 20-79 diagnosed with invasive or borderline ovarian cancer in three counties in Washington state in 1986-88, compared to 426 women randomly selected from the same counties, the number of births increasingly reduced the risk of ovarian cancer compared to no births. When the analysis was restricted to ever- pregnant women, a prior induced or spontaneous abortion (evaluated separately) was found not to be associated with the incidence of ovarian tumors, and was decreased only slightly in nulliparous women. It was concluded that, " it is possible that if incomplete pregnancies do affect the risk of ovarian cancer, their impact might be too small to be identified through epidemiologic studies."

"Epithelial Ovarian Cancer and the Ability to Conceive," A.S. Whittemore, M.L. Wu, R. S. Paffenbarger, Jr., D.L Sarles, J.B. Kampert, Cancer Research 49: 4047, July 15,1989.

In a case-control study of women in the San Francisco Bay area during 1983-85, ovarian cancer patients were more likely to be nulliparous (20.7%) compared to hospital controls (17.1%) or general population controls (10.0%). Ovarian cancer patients also had fewer number of term pregnancies (2.2) compared to hospital or general population controls (2.5) and had the same number of abortions (0.6) compared to controls.

"Personal and Environmental Characteristics Related to Elithelial Ovarian Cancer. I Reproductive and Menstrual Events and Oral Contraceptive Use," M.L. Wu, A.S. Whittemore, R.S. Paffenbarger, Jr., D.L. Sarles, Am. J. Epidemiology 128(6):1216,1988.

In two case-control studies in the San Francisco Bay area during 1974-77 and 1983-85, women having epithelial ovarian cancer had a similar number of reported abortions as controls. It was not specified whether the abortions were spontaneous or induced. Cases were more likely than controls to have been nulliparous.

"Reproductive. Genetic and Dietary Risk Factors for Ovarian Cancer," M. Mori, I. Harabuchi, H. Miyake, J. T. Cassagrande, B.E. Henderson, Am.J. Epidemiology 128(4): 771,1988.

A case-control study in Hokkaido, Japan during 1980-86 found that ovarian cancer risk was increased in single women, and in women with a family history of breast, uterine or ovarian cancer in a mother or sister. The risk was decreased in women who had experienced a live birth (OR 0.2, 0.1-0.6, 95% C.I.), an induced abortion (OR 0.5, 0.3-0.9, 95% C.I.), or in women who had permanent sterilization by tubal ligation (OR 0.4, 0.1-0.8, 95% C.I). Each of the reproductive factors remained significant when adjusted for each other using logistic regression analysis. The odds ratio for ovarian cancer decreased significantly with increasing number of live births. Compared with nulliparous subjects, women with 1 or 2 children had a third of the risk of ovarian cancer, women with 3-4 children had one-fourth the risk, and women with 5 or more children had l/20th the risk.

"Case-Control Study of Borderline Ovarian Tumors: Reproductive History and Exposure to Exogenous Female Hormones," B.L. Harlow, N.S. Weiss, G.L. Roth, J. Chu, J.R. Daling, Cancer Research 48: 5849, October 15,1988.

In a case-control study of women in three urban counties in Washington State during 1980-85, the risk of ovarian tumors among women who had given birth to 1 or 2 children and to 3 or more children was 0.7 and 0.4 respectively compared to that of nulliparous women. After adjusting for parity, a history of lactation reduced risk of ovarian cancer by 50%. After adjusting for age and gravidity (from 1 to 4), a similar number of cases and controls reported an induced abortion although it was not statistically significant. More cases than controls reported a history of a prior miscarriage.

"Parity, age at first childbirth, and risk of ovarian cancer," H-O Adami et al, The Lancet 344, November 5, 1994 p.1250-1254.

A case-control study of Swedish women born between 1925 and 1960 diagnosed 3486 cases of invasive ovarian cancers including 2992 epithelial, 300 stromal, 149 germ-cell, and 15 not classifiable plus 510 tumors of borderline malignant potential up until 1984. After simultaneous adjustment for parity and age at first birth, increasing parity was associated with a pronounced consistent decrease in relative risk of all invasive cancers, but a less consistent decrease for borderline tumors.

"Reproductive and Other Factors and Risk of Epithelial Ovarian Cancer: An Australian Case-Control Study," D Purdie et al, Int'l Journal of Cancer 62:678, 1995.

824 cases of women diagnosed with epithelial ovarian cancer in Queensland, New South Wales and Victoria, Australia between 1990-1993 were compared to 860 controls drawn at random from the electoral roll and stratified by age and geographic region. A reduced risk of ovarian cancer was found to be associated with increasing parity, but there were no associations between the development of ovarian cancer and the number of incomplete pregnancies.)

Endometrial Cancer

"Epidemiology and Primary Prevention of Cancers of the Breast, Endometrium, and Ovary," JL Kelsey and AS Whittemore, Ann Epidemiol 4:89-95, 1994.

Most of the risk factors indemnified for endometrial cancer involve exposure to estrogen with insufficient cyclic exposure to progesterone, and this explanation is generally accepted as a major etiologic pathway for the development of endometrial cancer.

"Is the Risk of Cancer of the Corpus Uteri Reduced by a Recent Pregnancy? A Prospective Study of 765,756 Norwegian women," G Albrektsen et al, Int'l J Cancer 61:485, 1995.

A study of 765,756 Norwegian women representing 9,307, 118 person years in the age interval of 30-56 years was undertaken using various registries. Compared to women with one full term pregnancy, nulliparous women had an increased risk of endometrial carcinoma. There was a reduced risk of endometrial carcinoma with an increasing number of full term pregnancies. The risk of endometrial carcinoma increased with increasing time since last birth. The reduction in risk among parous women compared to nulliparous women diminished with increasing time since last birth. The researchers concluded that, " our results support the hypothesis that the reduction in risk of endometrial carcinoma associated with a pregnancy is related to a mechanical shed of malignant or pre-malignant cells at each delivery."

"A Case-Control Study of Endometrial Cancer in Relation to Reproductive, Somatometric, and Life-Style Variables," A Kalandidi et al, Oncology 53:354, 1996.

A hospital-based case control study of cancer of the endometrium was conducted in Athens, Greece from 1992-94 by researchers at the University of Athens Medical School and the Harvard School of Public Health. It was found that the risk of endometrial cancer decreased with the number of live births but did not decrease with one miscarriage or one induced abortion.

"Reproductive, menstrual, and medical risk factors for endometrial cancer: Results from a case-control study," LA Brinton et al, Am J Obstet Gynecol 167:1317, 1992.

During 1987-90, a study was undertaken of 405 cases of newly diagnosed cancer of the uterine corpus in women between the ages of 20-74 years which were obtained from seven hospitals throughout the United States. Populations controls were matched for age, race, and location of residence obtained by random dialing techniques. The mean age of the cases at interview was 59.2 years compared to 58.0 for controls. Compared to women with no term births, the relative risk of endometrial cancer was significantly reduced with an increasing number of live births. The risk of endometrial cancer was the same for women reporting a prior induced abortion compared to women reporting not ever having an induced abortion. Women having one or two or more miscarriages had virtually the same risk as women reporting no miscarriages. It was concluded that the protective effect was limited to term births.

"Risk Factors for Endometrial Cancer," B. MacMahon, Gynecol. Oncol. 2: 122, 1974.

A case-control study of Boston area women found that nulliparity produces a twofold risk for endometrial cancer compared to women with one child, and a threefold risk compared to women with five children.

"The epidemiology of endometrial cancer in young women," B.E. Henderson, M.C. Pike, T. Mack, I. Rosario, Br. J. Cancer 47: 749,1983.

A case-control study of women age 45 years or less at diagnosis in Los Angeles County during 1972-79 found that increasing parity was strongly assodated with decreased risk for endometrial cancer. RR was 0.12 for women with three children compared to nulliparous women. Incomplete pregnancies (spontaneous and induced abortions) were associated with a slight decrease in risk (data not shown). 5.6 incomplete pregnancies were estimated to be equivalent to one full term pregnancy in terms of risk reduction but the decrease was not statistically significant.

"Reproductive Factors and Risk of Cancer of the Uterine Corpus: A Prospective Study," G. Kvale, I. Heuch, G. Ursin, Cancer Research 48: 6217,1988.

A prospective study of 62,079 Norwegian women diagnosed 420 cases of cancer of the uterine corpus from 1961-80. The risk of endometrial cancer decreased significantly with increasing parity. In parous women the odds ratio for those with 3 or more abortions vs. women not reporting abortion was 1.03 (0.58-1.82, 95% CI) after adjustment for parity, age at first birth in addition to demographic variables (unspecified).

"A Case-Control Study of Cancer of the Endometrium," J.L. Kelsey, V.A. LiVoIsi, T.R. Holford, D.B. Fischer, Am. J. Epidemiology 116(2): 1982.

A study of the epidemiology of endometrial cancer in women aged 47-74 in Connecticut from 1977-79, found that nulliparity and few pregnancies increased the risk of endometrial cancer.

"Epidemiology of Endometrial Cancer," M. Elwood, P. Cole, K.J. Roghman, S.D. Kaplan, J. National Cancer Inst. 59(4): 1055,1977.

In a study of Boston area women during 1965-69, married women with 1 or 2 children had a 0.6 relative risk of endometrial cancer, and women with 3 or 4 children had a 0.3 relative risk compared to married women who were nulliparous. No significant differences were noted between women with a history of stillbirth or miscarriage compared to women with no history of stillbirth or miscarriage.

Lung Cancer

Cigarette smoking is by far the most important important risk factor for lung cancer. The American Cancer Society estimated that 67,000 U.S. women will die from lung cancer in 1998. About 1 in 18 U.S. women will develop invasive lung and bronchus cancers in their lifetime. The 5- year survival rate for lung cancer is only 14%. In 1958-60, the rate of death from lung cancer of U.S. females was 5.5 per 100,000; By 1971-73, it had increased to 12.7 per 100,000; By 1991-93, it had risen to 32.9 per 100,000 and in 1994 was 42 per 100,000.

"Pregnancy Decision Making as a Significant Life Event: A Commitment Approach," J Lydon et al, Journal of Personality and Social Psychology 71(1): 141-151, 1996.

Women who were continuing their pregnancies to term reduced their smoking during pregnancy, while those who aborted did not reduce their smoking over time.

"Psychological responses following medical abortion (using mifepristone and gemepost) and surgical vacuum aspiration," R Henshaw et al, Acta Obstet Gynecol Scand73:812-818, 1994.

Postabortion anxiety scores at 16 days follow-up correlated with the number of cigarettes smoked, with the most anxious women having the heaviest smoking habits.

"Reproductive Patterns and Cancer Incidence in Women: A Population-Based Correlation Study in the USSR," L.I. Remennick, Int'l Journal Epidemiology 18(3): 498,1989.

A set of statistical tests was applied to assess associations between reproductive variables, including abortion, and lung cancer incidence among various regions in the USSR. A linear correlation coefficient of 0.42 was obtained with respect to lung cancer and abortion rate. A partial correlation coefficient of 0.36 was obtained with respect to lung cancer and abortion rate. (P=0.05). It was concluded that lung cancer was likely related to smoking.

"Stress and Smoking," Medical Times 114(2): 44, 1986.

A study at the University of New Hampshire linked high levels of social stress with high cigarette consumption and respiratory cancer deaths. One of the stress indicators was abortion. A stronger stress-lung cancer connection was found among women than among men although smoking and lung cancer death rates are higher in men. The researchers noted that many of the indicators used to measure stress, such as divorce and abortions could have a greater effect on women than men.

"Lung Cancer and Smoking Trends in the United States over the Past 25 Years," L. Garfinkel, E. Silverberg, CA-A Cancer Journal for Clinicians 41(3): 137, May/June, 1991.

According to the figures for the latest available year (1987) women smokers are at least 10.8 times more likely to die from lung cancer than women non-smokers.

"Smoking and women's health," ACOG educational bulletin, No 249, September, 1997, Int'l Journal of Gynecology & Obstetrics 60:71-82, 1997.

Since 1987, lung cancer has been the leading cause of cancer deaths among women. Women who smoke are 12 times more likely to die from lung cancer than those who never smoked. Citing American Cancer Society. Cancer facts and figures. (Atlanta: ACS, 1997) 5008

"Association of Induced Abortion with Subsequent Pregnancy Loss," Levin, JAMA243: 2495, June 27,1980.

A study of women patients entering Boston Hospital for Women during 1976-78 found that 31.7% smoked if there was no history of abortion, compared to 40.3% (one abortion) and 51.7% (two or more abortions).

"Outcome of first Delivery After 2nd Trimester Two-Stage Induced Abortion: A Historical Cohort Study," Meirick and Nygren, Acta., Obstet, Gynecol Scand. 63(1): 45,1984.

A Swedish study conducted during 1970-78 found that 37% of the women reporting prior abortion smoked 10 or more cigarettes per day compared to only 21.1% for parity matched controls and 18.9% for Swedish women generally. Heavier smoking was more pronounced among women with a history of abortion than for women with no history of abortion.

"Low Birth Weight in Relation to Multiple Induced Abortions," M.T. Mandleson, C.B. Madden, J.R. Daling, Am. J. Public Health 82(3):391, March 1992.

A study of 6,541 white women in major urban counties of Washington state who delivered during 1984-87 found that only 18.0% smoked during pregnancy if women reported no prior abortion compared to 28.1% (one abortion) or 41.6% (four or more prior abortions).

Colon and Rectal Cancer

"Is the Incidence of Colorectal Cancer Related to Reproduction? A Prospective Study of 63.000 Women," G. Kvale, I. Heuch, Int'l J. Cancer 47: 390,1991.

A Norwegian study of 63,090 women survey in 1956-59 and followed through 1980 found 581 cases of colon cancer and 250 cases of rectal cancer. High parity was not associated with reduced risk. Women who had two or more abortions compared to women with no abortions had an increased risk of both colon and rectal cancer ranging from 1.16-1.72 based upon logistic regression analysis taking into account date from al levels of the variables studied. The association was significant for rectal cancer only.

"Large Bowel Cancer in Relation to Reproductive and Hormonal Factors. A Case- Control Study," J. D. Potter, A..J. McMichael, J. National Cancer Institute 71(4): 703, October, 1983.

An Australian case-control study in 1979-80 of 99 cases of colon cancer and 56 rectal cancer compared to 311 controls found that colon cancer cases had more failed pregnancies, fewer live births (2.00 and fewer full-term pregnancies (2.1) compared to controls (2.6). Rectal cancer cases had almost the same number of live births (2.4) and full-term pregnancies (2.5) compared to controls (2.6).

"Incidence of Cancer of the Large Bowel in Women in Relation to Reproductive and Hormonal Factors," N.S. Weiss, J.R. Daling, W.H. Chow, J. National Cancer Institute 67(1): 57, July, 1981.

A study of women in Washington state from 1976-77 found that, on the average, women with colon cancer had given birth to fewer children than controls. Compared to nulliparous women, the incidence of colon cancer among women with 1 or 2 children was reduced 30% and among women with 3 or more children was reduced by 50%. The occurrence of pregnancy that was not full term did not differ between cases and controls.

"Age at First Pregnancy and Risk of Colorectal Cancer: A Case-Control Study," G.R. Howe, K.J. Craib, A.B. Miller, J. National Cancer Institute 74(6): 1155, June, 1985.

A Canadian study of women from Toronto and Calgary in 1976-78 found a strong protective effect of early age at first pregnancy for both colon and rectal cancers with little or no effect noted for the total number of pregnancies

"Children, Age at First Birth, and Colorectal Cancer Risk," Data from Melbourne Colorectal Cancer Study, G.A. Kune, S. Kune, L.F. Watson, Am. J. Epidemiology 129(3): 533,1989.

For colorectal cancer, the relative risk was 0.61 for those with one or more children compared with those with no children. The protection against colorectal cancer associated with having children and earlier age of birth of first child, was found to be similar for both males and females. This suggests that a life-style factor, as yet unidentified, is the mediator of these effects.

Other Cancers

"Reproductive Factors and the Risk of Hepatocellular Carcinoma in Women," C. LaVecchia, E. Negri, S. Franceschi, B. D'Avanzo, Int'l. J. Cancer 52: 351, 1992.

A hospital based case-control study in Northern Italy between 1984-91 found that the risk of liver cancer increased with parity. The relative risk for 1 or more induced abortions was 1.6 (0.7-3.6, 95% CD) and for two or more abortions was 2.1 (1.0-4.3, 95% CI) based upon estimates from multiple logistic regression equations.