Induced abortion as an independent risk factor for breast cancer

A comprehensive review and meta-analysis

Bibliographic Data

ID14622973
AuthorsJoel Brind (Baruch College), Vernon M Chinchilli (0000-0001-6488-7809, Baruch College), Walter B Severs (Pennsylvania State University), J Summy-Long, Joan Y Summy‐Long (Pennsylvania State University)
Year1996
Volume50
Issue5
Pages481-496
Publication date1996-10-01
Open AccessNo
TypeARTICLE
VenueJournal of Epidemiology and Community Health (JOURNAL)
Journal identifiersISSN: 0143-005X • E-ISSN: 1470-2738
PublisherBMJ (PUBLISHER • GB)
DOI10.1136/jech.50.5.481
PMID8944853
OpenAlexW2022370591
LanguageEN
Citations received18
References cited43

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

Abortion · Breast cancer · Cancer · Confidence interval · Gynecology · Incidence (geometry) · Meta-analysis · Obstetrics · Odds ratio · Pregnancy · Relative risk · Risk factor · Cancer Risks and Factors · Internal Medicine · Medicine · Reproductive Biology and Fertility · Reproductive System and Pregnancy

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