Postnatal Cardiometabolic Health After Metformin Use in Gestational Diabetes: A Secondary Analysis of the EMERGE Trial

Aim: Women with GDM display adverse lifetime cardio-metabolic health. We examined whether early metformin in GDM could impact cardio-metabolic risk factors postpartum. Research design & methods: EMERGE, a double-blind, placebo-controlled trial randomized pregnancies 1:1 to placebo or metformin at GDM diagnosis and followed participants from randomization until 12±4 weeks postpartum. In total 478 pregnancies were available for postpartum maternal assessment, 237 and 241 assigned to metformin and placebo respectively. Weight (kg), body mass index (BMI) (kg/m2), waist circumference (cm) and blood pressure (mmHg) were measured, infant feeding method documented and bloods drawn for a 75 gram oral glucose tolerance test, fasting insulin, C peptide and lipid analysis. Results: Despite similar weight and BMI at trial randomization, participants receiving metformin had significantly lower weight (79.5±15.9 vs 82.6±16.9kg; p=0.04) and BMI (29.3(5.6) vs 30.5(5.4); p=0.018) at the postpartum visit. However no difference in weight change from randomisation to 12 weeks postpartum was observed between metformin and placebo groups. Overall 29% (n=139) of the cohort met criteria for prediabetes or diabetes, with no positive impact with metformin. There were also no differences in measurements of insulin resistance, blood pressure or lipids between groups. Conclusion: Early metformin use in GDM did not impact important cardio-metabolic parameters in the early postpartum period despite significant benefits in weight gain and insulin use in pregnancy.