Effect of metformin on maternal and neonatal outcomes in pregnant obese non-diabetic women: A meta-analysis

Background: Metformin reduces maternal and neonatal weight gain in gestational diabetes mellitus; however, this effect is poorly investigated in non-diabetic women.
Objective: We performed this meta-analysis to investigate the effect of metformin intake during pregnancy on maternal and neonatal outcomes in obese non-diabetic women.
Materials and Methods: We searched Medline, EMBASE, and Cochrane CENTRAL for eligible randomized controlled trials addressing the efficacy of metformin in pregnant obese non-diabetic women. Data were extracted and analyzed using RevMan software (Version 5.3). Neonatal birth weight was the key outcome. Secondary outcomes included maternal weight gain, the incidence of preeclampsia, and neonatal adverse effects (miscarriage, stillbirth and congenital anomalies).
Results: Pooled data from two RCTs (n=843) showed that metformin caused a significant reduction in maternal gestational weight gain (MD-1.35, 95% CI: [2.08, -0.630]), compared to placebo. The summary effect-estimate did not favor either of the two groups in terms of reduction of neonatal birth weight Z score (MD-0.09, 95% CI: [0.23, 0.06]). Metformin was associated with 41% reduction in the risk of preeclampsia; however, this reduction was not statistically significant [RR 0.59, 95% CI: [0.03, 11.46]). None of the neonatal adverse events including stillbirth [RR 1.14, 95% CI: 0.42, 3.10]) and congenital anomalies (RR= 1.36, 95% CI: [0.58, 3.21]) differed significantly between the two groups.
Conclusion: For obese pregnant women, metformin could decrease gestational weight gain with no significant reduction in neonatal birth weight. In light of the current evidence, metformin should not be used to prevent poor pregnancy outcomes in obese non-diabetic women.