183-LB: A Randomized Placebo-Controlled Trial of the Effectiveness of Early Metformin in Addition to Usual Care in the Reduction of Gestational Diabetes Mellitus Effects (EMERGE)

The optimal approach to managing GDM is uncertain. We sought to determine whether early introduction of metformin (at diagnosis) plus lifestyle modification was superior to standard care (lifestyle modification alone). Methods: EMERGE is a phase III, superiority, parallel-group, 1:1 randomized trial comparing effectiveness of early metformin vs placebo initiated before 28 weeks +6 days. GDM was confirmed using WHO 2013 criteria. Metformin (or placebo) was initiated at 500mg/day titrated to 2500mg. The primary outcome was the composite of insulin initiation or fasting glucose ≥ 5.1 mmol/L at weeks 32 or 38. Results: Between June 2017-September 2022, 535 women were randomized, 268 to metformin, 267 to placebo; mean (SD) age of 34.3 (4.8), 23.7% primigravid, 17.6% non-Caucasian, 31.4% had prior GDM, 39.4% had BMI<30, mean gestation 25.4 weeks. There was no significant difference in the primary outcome between metformin and placebo treatments (56.8% vs 63.7%; RR=0.89 95%CI: 0.78-1.02). Insulin initiation was significantly lower in metformin (38.4%) vs placebo (51.1%) group (RR 0.75; 95%CI 0.62-0.91). Compared to placebo, metformin treated women achieved better glycemic control (HbA1C at 38 weeks; 33.9 vs 35 mmol/mol; P=0.004) and gained less weight between randomization and delivery (0.8kg vs 2.0kg; P=0.03), while infants were less likely to weigh >4000g (7.6% vs 14.8%; P=0.013). There was no significant difference in infants weighing <2500g (6.1% vs 3.4%; P=0.215), in infants needing NICU admission (15.3% vs 12.5%; P=0.439) or in infants born preterm <37weeks (9.2% vs 6.5%; P=0.329) in the metformin versus placebo groups. Conclusions: In a Phase III trial, early introduction of metformin did not reduce the composite of insulin initiation or elevated fasting glucose at week 32 or 38 in women with GDM, but was associated with important maternal and neonatal benefits with no increase in adverse perinatal events. Disclosure F. P. Dunne: None. A. Alvarez-Iglesias: None. C. Newman: None. A. Smyth: None. M. Browne: None. D. Devane: None. P. Gillespie: None. M. O'Donnell: None. Funding Health Research Board of Ireland