Skold C, et al. - Researchers studied the impact of pregnancy-related factors on epithelial ovarian cancer risk in this population-based case–control study. All parous women with epithelial ovarian cancer in Denmark, Finland, Norway and Sweden during 1967–2013 (n = 10,957) and up to 10 matched controls (n = 107,864) were included and by using conditional logistic regression, estimation of odds ratios (ORs) with 95% confidence intervals (CIs) was carried out. Findings revealed that not only high parity but also full-term pregnancies and pregnancies at older ages were related to decreased risk of ovarian cancer. The results support the cell clearance hypothesis, ie, a recent pregnancy provides protection by clearing of precancerous cells from the epithelium of the ovary/fallopian tubes, mediated by placental or ovarian hormones.