Polycystic ovary syndrome, gestational diabetes mellitus, and the mediating role of obesity: a population-based cohort study

This study evaluated the association between polycystic ovary syndrome (PCOS) and gestational diabetes mellitus (GDM), and the mediating effect of obesity. Included were 1,268,901 births, between 2006-2018 – 387,748 with maternal PCOS and 881,153 without. Modified Poisson regression generated a relative risk (aRR) adjusted for maternal covariates. Causal mediation analyses accounted for the indirect effect of obesity. Women with vs. without PCOS had a higher rate (60.2 vs. 48.6 per 1000 births) – and aRR (1.05, 95% CI 1.03, 1.06) of GDM. Obesity mediated a significant proportion (90%) of this association. Preconception counselling in patients with PCOS should target weight optimization.