Metformin Use During Pregnancy and Early‐Life Nutritional Status: A Systematic Review of Randomized Clinical Trials

BACKGROUND AND AIMS: Metformin is increasingly used to treat gestational diabetes mellitus and other insulin-resistant conditions during pregnancy. Because it crosses the placenta, concerns remain regarding its potential effects on offspring growth and metabolic programming. This systematic review evaluated the effects of prenatal metformin exposure on infant nutritional status and adiposity during the first year of life. METHODS: PubMed and Scopus were searched from inception through May 2026 for randomized controlled trials comparing metformin with placebo or standard care during pregnancy. Eligible studies reported infant nutritional status or adiposity-related outcomes from birth to 12 months. Risk of bias was assessed, and results were synthesized narratively. RESULTS: Eight publications from six randomized controlled trials were included. Birthweight and birth size classifications were the most frequently reported outcomes. Metformin was not consistently associated with differences in birthweight or other anthropometric measures. One trial reported lower birthweight, while two reported fewer large-for-gestational-age or macrosomic infants. No study assessed direct measures of infant adiposity. CONCLUSIONS: Current evidence does not consistently support an effect of prenatal metformin exposure on early infant anthropometry. Limited postnatal data and absent adiposity measures limit conclusions regarding postnatal growth and early metabolic programming and support standardized longitudinal body composition assessment.