Grand multiparity and reproductive cancer in the Jerusalem Perinatal Study Cohort

Grand multiparity is associated with reduced mortality from reproductive cancers. We aimed to separate the components of mortality, by measuring incidence of and survival after reproductive cancer onset in grand multiparous compared to other parous women. We linked data from the population-based Jerusalem Perinatal Study Cohort, which included women aged 13–55 who delivered 1964–1976, with Israel’s National Cancer Registry. We compared breast and gynecologic cancer risk and all-cause survival following a cancer diagnosis, among grand multiparae (GMPs = parity 5+, n = 8,246) versus women with parity 1–4 (n = 19,703), adjusting for reproductive and demographic variables. Grand multiparae were at significantly lower risk of breast cancer than others (adjusted hazard ratio (HRadj) = 0.62, 95 % confidence interval (CI) 0.54–0.71), after controlling for age at first birth, education, and other covariates. This reduction was greater among GMPs whose first birth occurred after age 30 (p-interaction = 0.0001) and for cancer occurring before age 50 years (p = 0.002). In contrast, GMPs were at greater risk of death than women with parity