SPONTANEOUS-ABORTION AND RISK OF FATAL BREAST-CANCER IN A PROSPECTIVECOHORT OF UNITED-STATES WOMEN

Controversy exists over the possible relationship between induced and spontaneous abortion and risk of breast cancer. Thus, the association of fatal breast cancer and spontaneous abortion was examined in a larg e prospective study of United States adult women. After seven years of follow-up, 1,247 cases of fatal breast cancer were observed among 579 ,274 women who were cancer-free at interview in 1982 and who provided complete reproductive histories. Results from Cox proportional hazards models, adjusted for other risk factors, showed no association betwee n a history of spontaneous abortion and risk of fatal breast cancer (r ate ratio [RR] = 0.89, 95 percent confidence interval [CI] = 0.78-1.02 ). The RR did not increase with increasing numbers of abortions. Parou s women who had a spontaneous abortion before their first term birth w ere not at increased risk compared with parous women with no history o f spontaneous abortion (RR = 0.76, CI = 0.54-1.05). Women whose only p regnancy ended in a spontaneous abortion were not at increased risk co mpared with women who were never pregnant (RR = 0.61, CI = 0.27-1.38) or whose only pregnancy ended in a livebirth (RR = 0.72, CI = 0.32-1.6 5). These findings do not support an association between spontaneous a bortion and fatal breast cancer.