“The totality of the worldwide epidemiological evidence indicates that pregnancies ending as either spontaneous or induced abortions do not have adverse effects on women’s subsequent risk of developing breast cancer”: This is the conclusion of an analysis of data from 53 studies of women with invasive breast cancer that included information on abortion history. (1) The studies took place in 16 countries with liberal abortion laws and included a total of about 83,000 women. In analyses pooling data from the 12 studies in which information about spontaneous abortion was recorded before women’s breast cancer was diagnosed (and which presumably suffer from less underreporting of abortion than those in which this information was collected retrospectively), the risk of breast cancer was statistically indistinguishable between women who had ever had a spontaneous abortion and those who had not. Thirteen studies reporting prospective data on induced abortion showed a small but statistically significant reduction in risk for women who had terminated a pregnancy. Results were similar regardless of women’s age, whether they had given birth, the number of abortions they had had or the timing of their abortions.