Metformin reduces maternal weight gain in obese pregnant women: a systematic review and meta‐analysis of two randomized controlled trials

Obese pregnant women are likely to face several gestational and neonatal complications. Metformin is an effective oral antihyperglycaemic agent that is considered to be effective during pregnancy. The aim of our study was to evaluate the effect of metformin on obstetric and perinatal outcomes in obese pregnant women. Electronic databases were searched (MEDLINE, EMBASE, Web of Science, Scopus, ClinicalTrials.gov, OVID, and Cochrane Library). The selection criteria included only randomized clinical trials (RCTs) of obese pregnant women randomized to a daily metformin regimen or to a placebo condition. The type of participants included women with a body mass index (BMI) ≥ 30 kg/m2 who did not have diabetes mellitus, any other disease, or a contraindication to metformin use. The summary measures were reported as relative risk (RR) with 95% confidence intervals (CIs). The primary outcome was the effect on maternal weight gain (MWG). Two double-blind RCTs, including 849 obese pregnant women, were included in the meta-analysis: 428 (50.4%) were randomized to the metformin group, and 421 (49.6%) were randomized to the placebo group. The use of metformin was significantly associated with lower MWG. Metformin was also associated with a significantly lower incidence of preeclampsia (PE) and admission to the neonatal intensive care unit (NICU). Metformin could be considered a useful drug for the treatment of obese, nondiabetic pregnant women because it can significantly decrease weight gain in pregnant women and improve perinatal outcomes by reducing the incidence of PE and NICU admission. However, women should be aware of the uncertainties concerning the long-term effects of metformin transplacental passage on metabolic outcomes.