Induced Abortion and Breast Cancer Risk: A Critical Analysis of the Report of the Harvard Nurses Study Ii (Clinical Report‪)‬

An April 24th paper by Harvard researchers Karin Michels et al. (1) reported the widely disseminated conclusion: "Among this predominantly premenopausal population, neither induced nor spontaneous abortion was associated with the incidence of breast cancer." This conclusion was based on the results of 10 years of follow-up of participants in the Harvard Nurses Study II, between 1993 and 2003. Data were gathered from baseline questionnaires returned by more than 105,000 women in 1993, and every two years thereafter by women who were 39-56 years of age in 2003. Results from this cohort analysis were presented as Hazard Ratios (HR), with the overall, covariate-adjusted HR for induced abortion being 1.01, 95 %confidence interval (CI): 0.88-1.17.