DECIDE: A Comparative Effectiveness Trial of Metformin Versus Insulin for the Treatment of Gestational Diabetes

Gestational diabetes mellitus (GDM) is one of the most common medical complications of pregnancy. Glycemic control decreases the risk of adverse pregnancy outcomes for the pregnant individual with GDM and the infant exposed in utero (1). One in four individuals with GDM will require pharmacotherapy to achieve glycemic control. Insulin has been the mainstay of pharmacotherapy. Metformin is an alternative option increasingly used in clinical practice (2). Both insulin and metformin reduce the risk of adverse pregnancy outcomes, but comparative effectiveness data from a well-characterized, adequately powered, and diverse U.S. population remain lacking (3). Because metformin crosses the placenta, long-term safety data, in particular the risk of childhood obesity, from exposed children are also needed. In addition, the patient-reported experiences of individuals with GDM requiring pharmacotherapy remains to be characterized, including barriers for and facilitators of metformin versus insulin use. In a two-arm open-label, pragmatic comparative effectiveness randomized controlled trial (RCT), the DECIDE Study will examine whether metformin is not inferior to insulin in reducing adverse pregnancy outcomes and is comparably safe for exposed mothers and children, and whether patient-reported factors, including facilitators of and barriers to use, differ between metformin versus insulin use. The DECIDE Study Consortium will recruit and retain 1,572 pregnant individuals with GDM who need pharmacotherapy at 20 U.S. sites to metformin versus insulin and follow them and their children through delivery and then to 2-years Primary aim: To evaluate whether outcomes in pregnant individuals randomized to metformin are not inferior to those in pregnant individuals randomized to insulin for the composite adverse neonatal outcome defined as large-for-gestational-age birthweight (LGA), hypoglycemia, hyperbilirubinemia, or death. Secondary aims: 1. To evaluate whether mean child body mass index (BMI) at 2 years of age is higher in the offspring of pregnant individuals randomized to metformin. 2. To conduct a qualitative or mixed-methods analyses on a subgroup of participants to understand facilitators and barriers associated with metformin versus insulin use and heterogeneity of treatment effects (HTE) to facilitate evidence-based pharmacotherapy. 3. To evaluate whether pregnant individuals randomized to metformin have equivalent maternal (hypertensive disorder of pregnancy, gestational weight gain, mode of delivery, and obstetric anal sphincter injuries) and neonatal (preterm birth, mechanical ventilation, NICU admission, oxygen support, and respiratory distress syndrome) outcomes. 4. To evaluate whether pregnant individuals randomized to metformin have equivalent maternal (obesity, anthropometry, adiposity, diabetes, hypertension, cholesterol, and metabolic profile) and child (obesity, anthropometry, and adiposity) outcomes at 2-years postpartum. 5. To evaluate whether pregnant individuals randomized to metformin have equivalent patient-reported outcomes (PROs), as measured at 6 weeks postpartum and at 2 years postpartum.