BJOG

Metformin in PCOS pregnancy: Fewer maternal infections, but more childhood allergies

August 20, 2025

Study details: This post hoc analysis combined data from two randomized trials (PregMet and PregMet2) and one follow-up study (PedMet), involving 634 pregnant women with PCOS and 145 offspring. Participants were randomized to receive metformin (1700–2000 mg/day) or placebo from the first trimester to delivery. Maternal infections and allergic conditions in offspring were assessed using logistic regression, with BMI and infection status evaluated as potential modifiers or mediators.

Results: Metformin significantly reduced maternal infections during pregnancy (odds ratio, 0.68), particularly viral infections (OR, 0.71). However, offspring exposed to metformin in utero had increased odds of developing allergies (OR, 4.83) and eczema (OR, 2.42) by age 8. Maternal BMI and infection status didn’t mediate these associations.

Clinical impact: While metformin may offer protective effects against maternal infections in PCOS pregnancies, clinicians should weigh these benefits against the elevated risk of allergic conditions in offspring. These findings underscore the need for long-term pediatric follow-up and informed counseling when prescribing metformin during pregnancy.

Source:

Ryssdal M, et al. (2025, August 11). BJOG. Metformin Treatment in PCOS Pregnancies Reduces Maternal Infections and Increases the Risk of Allergies and Eczema in the Offspring: Post Hoc Analyses of Two Randomised Controlled Trials and One Follow-Up Study. https://pubmed.ncbi.nlm.nih.gov/40785326/