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The Research

Note: Not all women who develop breast cancer have had an induced abortion nor do all women who have an induced abortion develop breast cancer.

Induced abortion is the most preventable risk factor for breast cancer. Women who experience abortion are at greater risk for developing the deadly disease. The correlation of human research (1-8) with data obtained in rodent experimental models (9) lends support to the biological explanation of the Abortion Breast Cancer (ABC) link. In addition a large body of epidemiological research has repeatedly established that induced abortion does, in fact, lead to greater risk of breast cancer in women. Although research also exists that seeks to undermine or deny that there is a link, a close look at much of the research in question shows evidence of unacceptable and unscientific research methods, which in turn results in questionable conclusions.

Research that Supports the Link Between Abortion and Breast Cancer

Research that Denies the Link Between Abortion and Breast Cancer

Research Reviews

For More Information

Research that Supports the Link Between Induced Abortion and Breast Cancer

    • Since 1957, a total of 70 studies worldwide have been published with specific data on induced abortion and breast cancer. Of these, approximately 80% have provided evidence linking induced abortion to the later development of breast cancer. For a review of the evidence please see the abortionbreastcancer.com website.
    • A 1996 meta-analysis of the abortion/breast cancer data, Brind et al, found that there was a significant independent risk for breast cancer associated with induced abortion. This review of many studies demonstrated that not only did induced abortion increase a woman’s risk for breast cancer by denying her the protective effects of full-term pregnancy and breastfeeding, but that the abrupt, unnatural termination of the pregnancy itself, caused an increased risk. The findings concluded that an induced abortion elevates a woman’s overall risk of developing breast cancer by 30 percent.(10)

    • In the Fall 2007 issue of the Journal of American Physicians and Surgeons, British breast cancer researcher and statistician Dr. Patrick Carroll published a study which reinforced that in predicting female breast cancer incidence in eight European countries, among seven risk factors,  “Induced abortion is found to be the best predictor, and fertility is also a useful predictor.”(11)
    • Dr. Carroll's research showing that abortion is the “best predictor of British breast cancer trends” was presented in Paris on September 7, 2005 at a conference sponsored by the National Institute for Demographic Studies. Carroll is Director of the London-based Pensions and Population Research Institute.

      Patrick Carroll revealed three trends in breast cancer incidence associated with abortion:
      Trend #1: British upper class women are more likely to develop breast cancer and to die of the disease.
      Trend #2: Variations in breast cancer rates across the British Isles can be explained by differences in the abortion rate. Ireland, where abortion is prohibited, has the lowest incidence of breast cancer. The highest rate of breast cancer is in London and the Southeast where abortion is most prevalent.
      Trend #3: Breast cancer rates increased approximately 70% between 1971 and 2002. Carroll studied breast cancer rates for women ages 50-54 born in the years 1926-1946 and found that breast cancer rates were highly correlated with abortion rates and less highly correlated with fertility and other factors.

      “Carroll’s research is significant because he used national data reporting breast cancers and abortions,” writes Coalition on Abortion/Breast Cancer President Karen Malec. “Therefore, it's free of any possibility of a hypothetical problem called ‘recall bias.’ Opponents of the abortion-cancer link have never provided credible evidence of recall bias. Nevertheless, they claim that research depending on interviews with women to report their abortion histories is flawed because more cancer patients than healthy women accurately report their abortions.” This claim has repeatedly been proven to be false.

    • Carroll's earlier predictions using the same mathematical model have proven quite accurate for predicting cancers in England and Wales, observed from 1998-2004. (12)
    • A December 2001 British study by Carroll, revealed that abortion doubles a woman’s risk of developing breast cancer. Dr. Carroll predicted a surge in the number of breast cancer cases for women of all ages as a result of the high number of abortions performed on women who have never carried a child to term. 13

      For more information, please see Patrick Carroll’s press release at: http://www.abortionbreastcancer.com/press_releases/PatrickCarroll0509.PDF

    • A November 1994 study by Dr. Janet Daling found that overall, women who abort their first pregnancy increase their chance of developing breast cancer by 50 per cent. (14)
    • The book published by the deVeber Institute for Bioethics and Social Research entitled “Women’s Health after Abortion The Medical and Psychological Evidence” (Second Edition) by Canadian authors Elizabeth Ring-Cassidy and Ian Gentles devotes a whole chapter to the research on the link between induced abortion and breast cancer. Click here to read chapter two of this book on the deVeber Institute's website.
    • Breast surgeon Dr. Angela Lanfranchi has written an article which summarizes the evidence linking induced abortion and breast cancer and the biological basis for the association. Click here to view a pdf. copy of this article: The Abortion-Breast Cancer Link, Ethics and Medics, January 2003
    • The 1998 first World Conference on Breast Cancer held in Kingston, Ontario acknowledged the link between abortion and breast cancer in its Global Action Plan Report:

      “Today, women in general are exposed to higher levels of estrogen during their lifetime than was the case in previous generations. It is believed that women now face excess levels of both natural and synthetic estrogens, increasing their risk of breast cancer. Prolonged use of the birth control pills, late or lack of pregnancies and breast- feeding, INDUCED TERMINATION OF PREGNANCIES (emphasis added), a diet high in fat, meat or dairy products, and hormone replacement therapy following menopause, all are cited as risk factors for increased estrogens and breast cancer.”

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Research that Denies the Link Between Induced Abortion and Breast Cancer

    Critique: While this conclusion was based on 10 years of follow-up of the large Harvard Nurses Study II group, Dr. Joel Brind has exposed several serious methodological concerns which “cast doubt on the validity of the overall results.”(16).  The “failure to exclude recent exposures (to abortion), coupled with failure to include many appropriate cases and to apply appropriate statistical adjustments, all combine to lower the observed association” (39), a situation Brind characterizes as a “strong and pervasive bias” (39).  Brind argues that with the appropriate adjustments to these data, it would reveal an increase in breast cancer risk ranging from 20-50% (39). 

    • The 2008 “California Teachers Study” (17) published in the journal Contraception,  acknowledges the biological explanation supporting a link between abortion and breast cancer.  The authors conclude however, that “we found no statistically significant association between any measure of incomplete pregnancy and breast cancer risk...” (391).
    Critique: Inappropriate comparisons were made, comparing women who had aborted their pregnancies to those who had never been pregnant.  Childlessness raises breast cancer  risk, and this invalid comparison would minimize a positive finding with abortive women.  The authors also merged induced and spontaneous abortion, which are biologically distinct events.  Spontaneous abortion, especially early in pregnancy, is associated with lower than normal levels of  pregnancy hormones, due to either a fetal or ovarian abnormality.
    • The 1997 Melbye et al. study (18) is often touted as an authoritative study proving that there is no link between abortion and breast cancer. According to researcher, Joel Brind, this study contains "such substantial departures from proper statistical analysis as (1) the breast cancer (the outcome variable) registry's antedating (emphasis in original) the abortion (exposure variable) registry by up to 5.5 years, and (2) the misclassification of some 60 000 women as not having had abortions, who actually had legal abortions on record" (10). Even with these major methodological flaws, and even though in the body of the Melbye study text it mentions that "with each one-week increase in the gestational age of the fetus, there was a 3 percent increase in the risk of breast cancer" (18) and that in pregnancies that were aborted after 18 weeks gestation, there was a statistically significant 89% risk elevation, this study is consistently put forward as proof that there is no association between abortion and breast cancer.

      Recall Bias

      Those who assert that induced abortion does not increase breast cancer risk, often postulate recall (or reporting) bias in the literature as being responsible for the appearance of a positive link. According to the recall bias hypothesis, when women are interviewed, those with breast cancer are more likely to reveal they had an abortion than those who have not had breast cancer.

      The first paper which claimed evidence of recall bias was a 1991 Swedish study.(19) This study initially concluded that 50% of women without breast cancer had under-reported their abortions, while it was assumed that 27% of the women in the study were "over-reporting" their abortions, because they were not recorded in the abortion registry used by the authors. The often referred to recall bias hypothesis is based solely on the purported results of the Swedish study. However, an analysis of the same data by a research group led by Janet Daling revealed the percentage of under-reporting to actually be a mere 16%, and not statistically significant. Daling also doubts the concept of "over-reporting", as she states, "we believe that it is reasonable to assume that virtually no women who truly did not have an abortion would claim to have one” (14) In a published letter (20), the authors of the Swedish study acknowledged the claim of "over-reporting" to be unfounded, and with that all significant evidence of recall bias evaporates. They concede that "we are not surprised to find some Swedish women confidentially reporting having had induced abortions during the period 1966-74 that are not recorded as legally induced abortions…Some women therefore had induced abortions abroad or unrecorded terminations of pregnancy"(20).

      The recall bias hypothesis has been tested by retrospective studies comparing case-interview responses to corresponding clinical records in which competent obstetricians document induced abortions and miscarriages. In one study (21) researchers found the same risk of breast cancer when they used medical records as when they used retrospective interviews of the same patients proving, once again, that recall bias did not exist.(22)

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Research Reviews

In the Winter 2005 issue of the Journal of American Physicians and Surgeons, Dr. Joel Brind published a review of ten prospective studies published between 1996 and 2005 (18).  While all of the reviewed studies conclude that there is no link between induced abortion and breast cancer, Brind maintains that they embody many serious methodologic weaknesses and flaws, including “cohort effects, substantial misclassification errors due to missing information in databases, inadequate follow-up times, inadequately controlled effects of confounding variables, and frank violations of the scientific method (105)”.  He concludes that the flaws are “sufficient to invalidate their findings”(109), and that “these recent studies therefore do not invalidate the large body of previously published studies that established induced abortion as a risk factor for breast cancer” (105). View complete review here: http://www.jpands.org/vol10no4/brind.pdf

For more information

    • A summary of all the research available on the link between abortion and breast cancer is available at: www.abortionbreastcancer.com. We wish to thank Karen Malec and her team for the excellent research and website which they have compiled and continue to update.
    • More information is also available from the Breast Cancer Prevention Institute. We are also grateful to Dr. Joel Brind for his assistance and advice in preparing this website.

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References

(1) Dickson RB, Russo J. Biochemical Control of Breast Development. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast, 2nd ed. Philadelphia: Lippincott, Williams and Wilkins 2000: 15-31.
(2) Salazar H, Tobon H. Morphologic Changes of the Mammary Gland During Development, Pregnancy and Lactation. In: Josimovich J, ed. Lactogenic Hormones, Fetal Nutrition and Lactation. New York: Wiley, 1974: 221-227.
(3) Drife JO. "Breast Development in Puberty". In: Angeli A Breadlow HL, and Dogliottti, eds. Annals of the New York Academy of Sciences, vol 464. Endocrinology of the Breast: Basic and Clinicla Aspects. New York: New York Academy of Sciences 1986: 58-65.
(4) Russo J, Lynch H, Russo IH. Mammary Gland Architecture as a Determining Factor in the Susceptibility of the Human Breast to Cancer. Breast Journal 2001; 7(5): 278-291.
(5)Russo J, Russo IH. Development of the human breast. Maturitas 2004; 49(1): 2-15.
(6) Russo J, Mailo D, Yun-Fu Hu, et al. Breast differentiation and its implication in cancer prevention. Clinical Cancer Research. January 2005; 11: 931s-936s.
(7) Faber KA, Hammond CB. Endocrine Aspects of Breast Disease and Breast Function. In: Isaacs, ed . Textbook of Breast Disease. St. Louis, Missouri: Mosby-Year Book, Inc, 1992: 143-154.
(8) Russo J, Russo IH. Differentiation and breast cancer. Medicina (B Aires). 1997:57 Suppl 2: 81-91.
(9) Russo J, Russo IH. Susceptibility of the Mammary Gland to Carcinogenesis. II. Pregnancy Interruption as a Risk Factor in Tumor Incidence. American Journal of Pathology 1980 Aug; 100(2): 497-512. Russo J, Russo IH. Experimentally Induced Mammary Tumors in Rats. Breast Cancer Research and Treatment. 1996; 39(1): 7-20.
(10) Brind J, Chinchilli VM, Severs W, Summy-Long J. Reply: re: Relation Between Induced Abortion and Breast Cancer. Journal of Epidemiology and Community Health 1998; 52: 209-211
(11)
Patrick Carroll, "The Breast Cancer Epidemic: Modeling and Forecasts Based on Abortion and Other Risk Factors," Journal of American Physicians and Surgeons Fall 2007 12;3:72
(12) Carroll, P.  Pregnancy Related Risk Factors in Female Breast Cancer incidence.  International congress of Actuaries, Transactions 2002;4:331-375
(13) Carroll, P. "Abortion and Other Pregnancy-Related Risk Factors in Female Breast Cancer," Pension and Population Research Institute (PAPRI), 4 December 2001. Copies are available from PAPRI at 35 Canonbury Road, London, N1 2DG, UK.
(14) Daling JR, Malone KE, Voigt LF, White E, Weiss NS. Risk of Breast Cancer Among Young Women: Relationship to Induced Abortion. Journal of the National Cancer Institute 1994; 86: 1584-1592.
(15) Michels KB, Fei Xue MD, Colditz GA, Willett WC.  Induced and Spontaneous abortion and incidence of breast cancer among young women:  A prospective cohort study.  Arch Intern Med 2007;167:814-820
(16) Brind, J.  Induced Abortion and Breast Cancer Risk: A Critical Analysis of the Report of the Harvard Nurses Study II.  JpandS, Summer 2007. 12;2:38
(17) DeLellis Henderson K, Sullivan-Halley J, Reynolds P, Horn-Ross P, Clarke C, et al. Incomplete pregnancy is not associated with breast cancer risk: the California Teachers Study.  Contraception 2008;77:391-396
(18) Melbye M, Wohlfahrt J, Olsen JH, et al. Induced Abortion and the Risk of Breast Cancer. New England Journal of Medicine 1997; 336:81-85;
(19) Lindefors-Harris BM, Eklund G, et al. Response Bias in a Case Control Study Analysis Utilizing Comparative Data Concerning Legal Abortions for Two Independent Swedish studies. American Journal of Epidemiology 1991; 134: 1003-1008.
(20) Meirik O, Adami HO, Eklund G. Letter to the editor: Relation between induced abortion and breast cancer. Journal of Epidemiology and Community Health. 1998; 52: 209.
(21) Ye Z, et al. Breast Cancer in Relation to Induced Abortions in a Cohort of Chinese Women. British Journal of Cancer. 2002; 87(9) :977-981
(22) Lanfranchi A. The Abortion-Breast Cancer Link Revisited. Ethics and Medics 2004; 29(11): 1-4.
(23) Brind, Joel. “Induced Abortion as an Independent Risk Factor for Breast Cancer: A Critical Review of Recent Studies Based on Prospective Data”. Journal of American Physicians and Surgeons, Winter 2005  10; 4: 105-110