Twin births, sex of children and maternal risk of ovarian cancer: A cohort study in Norway

Abstract

In a follow-up of 1 208 001 women aged 20-74 years, no significant association was found between twin births (112 cases) and risk, though those with twin girls had a non-significantly higher risk than those with singleton births; among the latter, those with girls only had a higher risk of endometrioid tumours (incidence rate ratio 1.35; 95% confidence interval 1.03-1.76, based on 475 cases) than women with boys only. © 2007 Cancer Research.