Metformin in Pregnancy Study (MiPS): protocol for a systematic review with individual patient data meta-analysis

Introduction: Gestational diabetes mellitus (GDM) is a common disorder of pregnancy and contributes to adverse pregnancy outcomes. Metformin is often used for the prevention and management of GDM; however, its use in pregnancy continues to be debated. The Metformin in Pregnancy Study aims to use individual patient data (IPD) meta-analysis to clarify the efficacy and safety of metformin use in pregnancy and to identify relevant knowledge gaps. Methods and analysis: MEDLINE, EMBASE and all Evidence-Based Medicine will be systematically searched for randomised controlled trials (RCT) testing the efficacy of metformin compared with placebo, usual care or other interventions in pregnant women. Two independent reviewers will assess eligibility using prespecified criteria and will conduct data extraction and quality appraisal of eligible studies. Authors of included trials will be contacted and asked to contribute IPD. Primary outcomes include maternal glycaemic parameters and GDM, as well as neonatal hypoglycaemia, anthropometry and gestational age at delivery. Other adverse maternal, birth and neonatal outcomes will be assessed as secondary outcomes. IPD from these RCTs will be harmonised and a two-step meta-analytic approach will be used to determine the efficacy and safety of metformin in pregnancy, with a priori adjustment for covariates and subgroups to examine effect moderators of treatment outcomes. Sensitivity analyses will assess heterogeneity, risk of bias and the impact of trials which have not provided IPD