Metformin in pregnancy to avert gestational diabetes in women at high risk: Meta-analysis of randomized controlled trials

Abstract

Previous randomized and observational studies on the efficacy of metformin in preg-nancy to reduce incident gestational diabetes mellitus (GDM) in women at high risk(obesity, polycystic ovary syndrome [PCOS], or pregestational insulin resistance) havebeen conflicting and several groups are planning further randomized controlled trials(RCTs) to answer this question conclusively. This work assesses the efficacy of met-formin in pregnancy to avert one outcome-incident GDM in women at high risk.We included RCTs comparing metformin with usual care or placebo controls in termsof incident GDM and recruiting women at high risk during early pregnancy. Eleven eli-gible trials enrolled 2370 adult women whose intervention arm consisted of metfor-min started at conception or before 20 weeks of gestation. Risk of GDM wassimilar in intervention compared with controls (risk ratio [RR] 1.03; 95% confidenceinterval [CI], 0.85‐1.24). The data were of sufficient quality meeting the criteria forconsistency and directness. We conclude that metformin does not contribute toaverting the GDM outcome in women at high risk when initiated in pregnancy. Theevidence provided by this synthesis affirms that further broad clinical trials investigat-ing this question are no longer needed.