The presence of polycystic ovary syndrome increases the risk of maternal but not neonatal complications in women with type 2 diabetes in pregnancy.

Aims: Our aims were, in the setting of type 2 diabetes mellitus (T2DM) in pregnancy, to investigate the association of polycystic ovary syndrome (PCOS) with perinatal outcomes and to examine whether treatment with metformin had a differential effect in those with and without PCOS. Materials and Methods: We performed a retrospective cohort study using the metformin in women with type 2 diabetes in pregnancy (MiTy) trial data. We examined differences in maternal and neonatal outcomes among MiTy participants with and without PCOS using linear and logistic regression to adjust for potential confounders. We additionally examined the relative difference in the effect of metformin treatment on pregnancy outcomes among MiTy participants with PCOS versus those without PCOS. Results: Among women with T2DM in pregnancy, PCOS was significantly associated with higher excess gestational weight gain (unadjusted 12.0 vs. 11.4 kg, adjusted mean difference 2.1 kg [0.3, 3.9], p = 0.021) and higher total insulin dose at 34–36 weeks (unadjusted 172 vs. 124 units per day, adjusted mean difference 44 units [15, 73], p = 0.004), but no difference was seen in neonatal outcomes. Unlike the non‐PCOS subgroup, metformin treatment versus placebo in the PCOS subgroup was associated with an increase in extremely large‐for‐gestational‐age infants (28.6 vs. 14.0%, p = 0.008 for interaction) and an increase in worsened pre‐existing maternal hypertension (16.7 vs. 4.5%, p = 0.046 for interaction). Conclusions: Clinicians should be alerted to the potential for high insulin requirements and excess weight gain in pregnant patients with T2DM and comorbid PCOS. Moreover, metformin may not be as beneficial in this population as previously understood. [ABSTRACT FROM AUTHOR]