Metformin versus insulin for gestational diabetes: The reporting of ethnicity and a meta-analysis combining English and Chinese literatures

Conclusive information is lacking regarding the safety and efficacy of using metformin versus insulin in the treatment of gestational diabetes (GDM), with existing reviews providing conflicting conclusions for key outcomes. This updated and comprehensive meta-analysis is the first to include randomised controlled trials (RCTs) published in both English and Chinese. The increased coverage of the literature will help inform clinical decisions regarding the use of metformin to treat GDM. This study will also summarise the reporting of ethnicity by RCTs as there appears to be ethnic disparities in the rates of adverse pregnancy outcomes associated with GDM as well as response to metformin. PubMed, Embase, CENTRAL and China National Knowledge Infrastructure were searched for RCTs that compared metformin versus insulin for the treatment of GDM. Twenty-nine RCTs were included. Metformin was found to be at least comparable to insulin for key pregnancy outcomes, and lower in cost. 2/29 studies reported the number of participants from each ethnic group. The short-term data suggests that metformin is safe and effective for the management of GDM. Further follow-up studies are required to elucidate the longer-term effects of metformin exposure in-utero. We recommend that future RCTs discuss ethnicity when reporting baseline characteristics and results.