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 use d data from a population-based case-control study of breast cancer among wo men age 25-64 conducted between 1996 and 1998 in urban Shanghai to assess w hether a history of and the number of induced abortions were related to bre ast cancer risk. In-person interviews were completed with 1,459 incident br east cancer cases ascertained through a population-based cancer registry, a nd 1,556 controls randomly selected from the general population in Shanghai (with respective response rates of 91% and 90%), After adjusting for confo unding, there was no relation between ever having had an induced abortion a nd 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 o f premenopausal breast cancer (OR = 0.9, 95% Ct 0.6-1.4) or postmenopausal breast cancer (OR 1,3, 95% CI 0.8-2.3). These results suggest that a histor y of several induced abortions has little influence on breast cancer risk i n Chinese women. (C) 2001 Wiley-Liss. Inc.