Aim: To determine whether induced abortion (IA) increases breast cancer (BC) risk. Materials and
Methods: Apopulation-based case-control study was performed from Dec, 2000 to November, 2004 in Shanghai, China, whereIA could be verified through the family planning network and client medical records. Structured questionnaireswere completed by 1,517 cases with primary invasive epithelial breast cancer and 1,573 controls frequencymatchedto cases for age group. The information was supplemented and verified by the family planning records.Statistical analysis was conducted with SAS 9.0.
Results: After adjusting for potential confounders, inducedabortions were not found to be associated with breast cancer with OR=0.94 (95%CI= 0.79-1.11). Comparedto parous women without induced abortion, parous women with 3 or more times induced abortion (OR=0.66,95%CI=0.46 to 0.95) and women with 3 or more times induced abortion after the first live birth (OR=0.66,95%CI =0.45 to 0.97) showed a lower risk of breast cancer, after adjustment for age, level of education, annualincome per capita, age at menarche, menopause, parity times, spontaneous abortion, age at first live birth,breast-feeding, oral contraceptives, hormones drug, breast disease, BMI, drinking alcohol, drinking tea, takingvitamin/calcium tablet, physical activity, vocation, history of breast cancer, eating the bean.
Conclusions: Theresults suggest that a history of induced abortions may not increase the risk of breast cancer.