Childhood overweight, tallness and growth increase risks of ovarian cancer.

Background: Adult body size is related to ovarian cancer risks, but size in childhood may also influence risks. We investigated if childhood body mass index (kg/m(2)), height, and growth patterns were associated with ovarian cancer overall and by histologic subtypes, including effects of birthweight. Methods: A cohort of 155,958 girls from the Copenhagen School Health Records Register, born 1930 to 1989 with measured weights and heights from 7 to 13 years, were included. During follow-up, 1,041 ovarian cancers were recorded. Overweight was defined using International Obesity Task Force criteria. Cox regressions were performed. Results: Compared with non-overweight girls, at most ages girls with overweight had increased risks of ovarian cancer overall (HR range: 1.24-1.34), mucinous, endometrioid, and clear cell ovarian cancers, but not serous and other ovarian cancers. Childhood height had positive and significant associations with ovarian cancer overall (HR range: 1.07-1.10 per z-score) and the endometrioid subtype but not with the other subtypes. Adjusting for birthweight minimally altered the associations with childhood body size. In growth analyses, girls with overweight or who were tall at 7 and 13 years had increased risks of ovarian cancer overall compared with average-sized girls at both ages. Conclusions: Ovarian carcinogenesis is linked to childhood overweight, tallness, and growth, with variations across histological subtypes, suggesting that early life plays a role in the origins of this disease. Impact: These findings emphasize that healthy body size and growth during childhood are important as they may contribute to reducing ovarian cancer risks.