Abortion history and breast cancer risk: Results from the Shanghai breast cancer study

Studies of the association between induced abortion and breast cancer risk have been inconsistent, perhaps due to underreporting of abortions. Induced abortion is a well‐accepted family planning procedure in China, and women who have several induced abortions do not feel stigmatized. The authors used data from a population‐based case‐control study of breast cancer among women age 25–64 conducted between 1996 and 1998 in urban Shanghai to assess whether a history of and the number of induced abortions were related to breast cancer risk. In‐person interviews were completed with 1,459 incident breast cancer cases ascertained through a population‐based cancer registry, and 1,556 controls randomly selected from the general population in Shanghai (with respective response rates of 91% and 90%). After adjusting for confounding, there was no relation between ever having had an induced abortion and breast cancer (odds ratio [OR] = 0.9, 95% confidence interval [CI] 0.7–1.2). Women who had 3 or more induced abortions were not at increased risk of premenopausal breast cancer (OR = 0.9, 95% CI 0.6–1.4) or postmenopausal breast cancer (OR = 1.3, 95% CI 0.8–2.3). These results suggest that a history of several induced abortions has little influence on breast cancer risk in Chinese women. © 2001 Wiley‐Liss, Inc.