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There is very strong evidence in the world’s scientific medical literature that induced abortion constitutes a significant risk factor for future breast cancer. Is it a real risk that every woman considering elective abortion should be appraised of? Or is it simply an unproven threat thrown into the abortion arena to frighten pregnant women from making the "the choice"?

These are absolutely vital questions for any abortion inclined pregnant woman. The threat of breast cancer, surgery, radiation, chemotherapy, disfigurement, even death, hang on the correct answers.

We depend on "evidence based medicine" to guide us to valid conclusions on such issues.

Here is the evidence:

There are two pregnancy related independent risk factors for breast cancer established in the medical literature. The first is the protective effect of an early first full term pregnancy. The landmark study establishing this protective effect [MacMahon, et al, (1970) Bull WHO 43:209-221] is widely accepted in the medical world. MacMahon, and group reanalyzed their 1970 data [Trichopolous D, Hsieh C, MacMahon B, Lin T, et al,, Age at any Birth and Breast Cancer Risk, International J Cancer, 1983:31:70l-704], finding that each one year delay in the first full term pregnancy increased relative breast cancer risk by 3.5% (compounded). Obviously, aborting a first pregnancy eliminates the protective effect against breast cancer.

The second independent risk factor for breast cancer is induced abortion. As of March, 2002, there have been published in the worldwide medical literature 37 studies (including 15 American studies) reporting data on the risk of breast cancer among women with a history of induced abortion. 28 of these studies report increased risk. Thirteen of the 15 American studies report increased risk, 8 with statistical significance (at least 95% probability that the result is not due to chance) irrespective of age at first full-term pregnancy.

The relative risk increase of the 37 studies combined is 30%. (Note: this means that among aborted women there would be a 30% increase in breast cancer cases over what would normally be expected. In the current American abortion experience, this would result in approximately 5,000 additional cases of breast cancer per year in the U.S. FYI, there are about 190,000 new cases of breast cancer diagnosed in the US each year.)

Consider the implications of the study specifically funded by the United States National Cancer Institute to investigate the abortion/breast cancer link (Daling et al, l994, JNCI 86:1584-92). Janet Daling’s group found an overall 50% breast cancer risk by age 45 for women who have had an induced abortion. (What would it be by age 65??) American women today have an approximately 12% lifetime chance of developing breast cancer. It follows that those who have had an induced abortion will have an 18% lifetime chance of developing breast cancer. But the risk increases even more than 50% for certain subgroups. For example, among women with a family history of breast cancer (mother, grandmother, sister, or aunt), the increase in risk was 80%. If the woman had her abortion before she was18, the increase in risk was more than 100%! If the woman had both risk factors (family history, and abortion before 18), the risk was incalculably high, i.e., there were 12 such women out of 1800 in the study, and ALL TWELVE DEVELOPED BREAST CANCER BY AGE 45. This subgroup is too small to be "statistically significant," but surely it is "significant" if you are an abortion-minded 17 year old pregnant teenager with a family history of breast cancer – – – – or if you are a doctor counseling this teen about abortion risks- – – – or if you are the girl’s parent (or boyfriend) concerned for her ultimate welfare.

The only study yet published on American women which relied solely on data from medical records entered at the time of the abortion (and therefore immune to inaccurate interview material) reported a statistically significant 90% increase in breast cancer risk with induced abortion. (Howe et al (1989) Int J Epidemiol 18:300-4.)

Authoritative sources in the National Cancer Institute and in the American College of Obstetricians and Gynecologists generally will cite "recall bias" as the scientific reason that they trivialize or outright deny the scientific literature on the subject. They look upon these studies as flawed due to recall bias, and apparently not worthy of serious consideration.

So what is "recall bias," (also known as "reporting bias" or "response bias"), if it is so powerful that it negates 28 of 37 worldwide studies? It is a theory that presumes that in interview based studies, women who have breast cancer will be more honest when asked if they have ever had an abortion, while many women who do not have breast cancer will tend to simply "not recall" or "not report" if they ever had an abortion. The result of this "recall bias" would be studies showing a higher incidence of breast cancer in post abortion women. On this tenuous theory, the world’s literature is discounted as unreliable. Not good science. However, the assumption of "recall bias," once birthed, has taken on a life of its own, and it has become the rallying cry for those who wish to discredit the world’s literature on the subject.

How does induced abortion influence the development, in some women, of breast cancer? (And let it be known that miscarriage—also known as ‘spontaneous abortion’—has no demonstrated breast cancer link). We do not know for sure. However, there may be an endocrinological basis.

Consider the following facts: l. estrogen excess can be a promoter of breast cancer development. 2. By 12 weeks of pregnancy, the estrogen level is about 20 times increased over non-pregnant levels. (This is why pregnant ladies have nausea and vomiting) 3. This causes maximal proliferation of undifferentiated (not able to produce milk) breast cells. (This is why pregnant ladies have breast enlargement and tenderness) 4. When pregnancy goes to term, the cells mature, and begin to give milk. (And it is known that full term pregnancy reduces breast cancer risk. Lactation may confer additional protection.) 5. When pregnancy is suddenly interrupted by induced abortion, the estrogen levels drop precipitously, and these cells are left in an immature state which presumably is more vulnerable to cancer influences. 6. When a person experiences a spontaneous miscarriage, in almost all cases the pregnancy has produced a subnormal estrogen level which is not associated with increased breast cancer risk . There are current ongoing studies exploring the validity of this theory.

The world’s scientific literature on the subject, (28 of 37 world wide studies, and 13 of 15 American studies) sends a very strong message. Why, then, the deafening silence on the issue by America’s medical authorities?

"deafening silence" is far too mild a term. There is outright denial of the evidence: The ACOG's 2002 Compendium of Selected Publications, states (page 392) "Long term risks sometimes attributed to surgical abortion include potential effects on reproductive function, cancer incidence, and psychologic sequelae. However, the medical literature, when carefully evaluated, clearly demonstrates no significant negative impact on any of these factors with surgical abortion." In the March 2002 issue of Obstetrics and Gynecology Clinics of North America, there is a 10 page review article entitled "Risk factors for breast cancer." In this article, only the following sentence mentions abortion: "Much has been written regarding the risk of breast cancer and induced abortion; however, an analysis of current data reveals no relationship of induce abortion to breast cancer risk." All of this information is obviously contrary to the great majority of published evidence. On this vital issue, organized medicine, for reasons of its own, is apparently willing to ignore or deny the evidence. We find this unacceptable. Women’s health, even their lives, may be at risk.

Ultimately, evidence based medicine (and truth) will prevail—but too late for many women who are submitting to their elective abortions without any informed consent regarding breast cancer risk, and with the assurances of many of the leaders in women's health care (and the silence of other leaders) that they need not worry about such risk.

If the 28 of 37 worldwide studies, including 13 of 15 American studies, are correct, the physicians who have denied the abortion/breast cancer link, and also those who have conveniently ignored it, will stand guilty of an immense disservice to the women they purport to serve–especially to some of those who subsequently develop breast cancer.

Counselors or doctors dealing with a pregnant woman considering abortion can confidently inform her that:

  1. Interruption of her first pregnancy will remove the protective effect of the first full term pregnancy, and subject her to a small but real increased risk of developing breast cancer in the future.
  2. According to the only study yet published which was specifically funded by the United States National Cancer Institute to investigate the ABC link, (the Daling study), if a woman has a mother, sister, aunt or grandmother with breast cancer, she will increase her chance of getting breast cancer by 80%; if she is under l8, she will double her chance of getting breast cancer, and if both conditions pertain, her risk is much, much higher (12 of 12 in the Daling study). And all these cancers were diagnosed by age 45. This is not a scare tactic. This is a frightening fact.
  3. 75% of the world’s scientific literature on the subject, including 86% of the American scientific literature on the subject, agree with the conclusion that elective abortion results in a significant increase in the risk of developing breast cancer in later life.


Studies which show an increased risk of breast cancer after elective abortion:

  • Talamini et al. (1996) Eur J. Cancer 32A:303-10.  The role of reproductive and menstrual factors in cancer of the breast before and after menopause.
  • Wataname & Hirayama (1968) Nippon Rinsho 26:1853-9 (in Japanese, no abstract available).
  • Dviorinin & Medvedev (1978) Meth Prog Breast Cancer Epidemiol Res, Tallin 1978.  USSR Acad Sci pp 53-63 (In Russian).
  • Luporsi (1988) Br J Cancer 72-744-51.
  • Wu et al.  (1996) Br J Cancer 73:680-6.
  • Robertson C, Van Den Donk M, Primic-Zakelj, MacFarlane T, Boyle P.  The association between induced and spontaneous abortion and risk of breast cancer in Slovenian women aged 25-54.  Breast 2001; 10:291-8.
  • Pike et al. (1981).  Br Journal of Cancer 43.  Oral contraceptive use and early abortion as risk factors for breast cancer in young women.
  • Nishiyama (1982) Shikoku Ichi 38:333-43 (In Japanese).
  • Laing et al. (1993) J National Med Assoc. 85:931-9.  Breast cancer risk factors in African-American women:  the Howard University Tumor Registry experience.
  • Andrieu (1995)  Am J Epidemiol.  Sep:128(3):478-89.  A population-based case-control study of diet and breast cancer in Australia.
  • Bu et al. (1995) Am J Epidemiol 141:S85.
  • Brinton et al. (1983) Br Journal of Cancer 47:757-62.  Reproductive factors in the etiology of breast cancer.
  • Rosenburg et al. (1988) Am J Epidemiology 127:981:9.  Breast cancer in relation to the occurrence and time of induced and spontaneous abortion.
  • Marcus et al. Am J Public Health 1999 Aug; 89(8):1244-7.  Adolescent reproductive events and subsequent breast cancer risk.
  • Palmer et al.  (1997) Cancer Causes Control 8:841-9å.  Induced and spontaneous abortion in relation to risk of breast cancer.
  • Lazovich et al. Epidemiology 2000 Jan;11(1):76-80.  Induced abortion and breast cancer risk.
  • Daling et al.  J Natl Cancer Inst 1994 Nov 2;86(21):1584-92 and White et al. (1994) J Natl Cancer Inst 86:505-14.  Risk of breast cancer among young women: relationship to induced abortion.
  • Newcomb et al. (1996) JAMA 275:283-7.  Pregnancy termination in relation to risk of breast cancer.
  • Howe et al.  Int J Epidemiol 1989 Jun;18(2):300-4.  Early abortion and breast cancer risk among women under age 40.
  • Andrieu et al.  Br J Cancer 1995 Sep;72(3):744-51.  Familial risk, abortion and their interactive effect on the risk of breast cancer–a combined analysis of six case-control studies.
  • Hirohata at al. (1985) Natl Cancer Inst Monogr 69:187-90.  Occurrence of breast cancer in relation to diet and reproductive history; a case-control study in Fukuoka, Japan.å
  • Ewertz & Duffy (1988) Br J Cancer 68:99:104.  Risk of breast cancer in relation to reproductive factors in Denmark.
  • Lipworth et al. (1995) Int J Cancer 61:181-4.  Abortion and the risk of breast cancer: a case-control study in Greece.
  • Rookus & van Leeuwan.  J Natl Cancer Inst 88:1759-64.  Induced abortion and risk for breast cancer: reporting (recall) bias in a Dutch case-control study.
  • M. Segi, et al.  “An Epidemiological Study on Cancer in Japan.”  GANN, Vol 48, Supplement: April, 1957.  (abstract not available).
  • Le M-G, Bachelot A, Doyon F, Kramar K, Hill C.  Oral contraceptive use and breast or cervical cancer: Preliminary results of a French case-control study.
     In: Wolff F-P, Scott JS, eds.  Hormones . . . in human cancer aetiology. Amsterdam:Elsevier, 1984; 139-47.
  • < li>Laing AE, Bonney GE, Adams-Campbell L, et al.  Reproductive and lifestyle factors for breast cancer in African-American women.  Genet Epidemiol 1994;11:300 (abstract only).

  • Daling JR, Brinton LA, Voigt LF, Weiss NS, Coates RJ, Malone KE, Schoenberg JB, Gammon M.  Risk of breast cancer among white women following induced abortion.  Am J Epidemiol 1996;144:373-80.

    Studies which did not show an increased risk of breast cancer after elective abortion:

  • Sanderson M, Shu X-O, Jin F, Dai Q, Wen W, Hua Y, Gao Y-T, Zheng W.  Abortion history and breast cancer risk: results from the Shanghai breast cancer study.  Int J Cancer 2001;92:899-905.
  • Moseson et al.  (1993) Int J Epidemiology 22:1000-9.  The influence of medical conditions associated with hormones on the risk of breast cancer.
  • Melbye et al.  N Engl J Med 1997 Jan 9:336(2)81-5.  Induced abortion and the risk of breast cancer.
  • Burany (1979) Jugosl Genekol Opstet 19:237-47 (Serbo-Craot).
  • La Vecchia et al. (1993) Int J Cancer 53:215-9.
  • Zaridze et al. (1988) “unpublished” and referenced in Br J Cancer 72:744-51.
  • Adami et al. (1990) Br J Cancer 62:122-6.  Absence of association between reproductive variables and the risk of breast cancer in young women in Sweden and Norway.
  • Newcomb PA, Mandelson MT.  A record-based evaluation of induced abortion and breast cancer risk (United States).  Cancer Causes Control 2000;11:777-81.1.
  • Goldacre MJ, Kurina LM, Seagroatt V, Yeaates.  Abortion and breast cancer: a case-control record linkage study.  J Epidem Comm Health 2001;55:336-7.

[American Association of Pro-Life Obstetricians & Gynecologists, 3 July 02]