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The reputation of abortion as safe for women—which claim is explicitly part of the Roe v. Wade decision—has rightfully come under serious question for many reasons over the years since Roe. One of the reasons that “safe abortion” has come under question is the evidence linking abortion to an increased risk of breast cancer (ABC link). The ABC link has been an issue that has been in and out of the limelight in recent years. It is an issue which has stubbornly refused to go away despite recurrent pronouncements from high places of its nonexistence. A recent example is a 2004 article in the prestigious British medical journal The Lancet.1 The paper was promoted by the mainstream media as “a full analysis of the current data.”2 According to the byline on the paper, the results of all these studies were compiled into a “collaborative reanalysis,” by the “Collaborative Group on Hormonal Factors in Breast Cancer,” a group of authors too numerous to list. However, a small print footnote reveals that the study was actually put together by a group of five scientists at Oxford University, headed by prominent British epidemiologist Valerie Beral. The Beral study’s conclusion is unequivocal: “Pregnancies that end as a spontaneous or induced abortion do not increase a woman’s risk of

STUDY OBJECTIVE: To ascertain, from the published reports to date, whether or not a significantly increased risk of breast cancer is specifically attributable to a history of induced abortion, independent of spontaneous abortion and age at first full term pregnancy (or first live birth); to establish the relative magnitude of such risk increase as may be found, and to ascertain and quantify such risk increases as may pertain to particular subpopulations of women exposed to induced abortion; in particular, nulliparous women and parous women exposed before compared with after the first full term pregnancy. INCLUDED STUDIES: The meta-analysis includes all 28 published reports which include specific data on induced abortion and breast cancer incidence. Since some study data are presented in more than one report, the 28 reports were determined to constitute 23 independent studies. Overall induced abortion odds ratios and odds ratios for the different subpopulations were calculated using an average weighted according to the inverse of the variance. An overall unweighted average was also computed for comparison. No quality criteria were imposed, but a narrative review of all included studies is presented for the reader's use in assessing the quality of individual studies. EXCLUDED STUDIES: All 33 published reports including data on abortion and breast cancer incidence but either pertaining only to spontaneous abortion or to abortion without specification as to whether it was induced or spontaneous. These studies are listed for the reader's information. RESULTS: The overall odds ratio (for any induced abortion exposure; n = 21 studies) was 1.3 (95% confidence interval of 1.2, 1.4). For comparison, the unweighted overall odds ratio was 1.4 (1.3,1.6). The odds ratio for nulliparous women was 1.3 (1.0,1.6), that for abortion before the first term pregnancy in parous women was 1.5 (1.2,1.8), and that for abortion after the first term pregnancy was 1.3 (1.1,1.5). CONCLUSIONS: The results support the inclusion of induced abortion among significant independent risk factors for breast cancer, regardless of parity or timing of abortion relative to the first term pregnancy. Although the increase in risk was relatively low, the high incidence of both breast cancer and induced abortion suggest a substantial impact of thousands of excess cases per year currently, and a potentially much greater impact in the next century, as the first cohort of women exposed to legal induced abortion continues to age.

Data were analyzed from 918 women aged 20-54 years at diagnosis with invasive breast cancer during 1986-89. The women had initially enrolled in a population-based case-control study investigating oral contraceptive use and the risk of breast cancer. Each case was pair-matched according to age and region of residence and cases and controls interviewed at home. Among parous women a history of induced abortion was associated with a 90% increased risk of breast cancer. Among nulliparous women no association was found between induced abortion and breast cancer. Neither among parous women nor nulliparous women was a history of spontaneous abortion related to the risk of breast cancer. The association between induced abortion and breast cancer was stronger in the southeastern regions of the country where there is a predominantly Roman Catholic population suggesting reporting bias. Support for reporting bias as an explanation for regional differences was also found in data supplied by study participants and their physicians on the use of oral contraception. The authors conclude that reporting bias is a real problem in case-control studies of induced abortion and breast cancer risk if study findings are based solely upon information from study subjects.