Comparison of Two Screening Strategies for Gestational Diabetes (GDM2) Trial: Design and rationale

Gestational diabetes mellitus (GDM) affects approximately 5 to 7% of pregnancies and is associated with increased risk for fetal overgrowth, cesarean delivery, birth trauma, and pre-eclampsia. GDM is commonly diagnosed in the US using a two-step screening and confirmatory approach, whereas a one-step approach is commonly used outside the US. Recent guidelines have suggested that the one-step approach should be used to diagnose GDM, although concern that this may increase the prevalence of GDM to approximately 18%—as well as the lack of clinical trials-based evidence regarding the difference in perinatal outcomes–has led to skepticism about adopting the one-step approach. The Comparison of Two Screening Strategies for Gestational Diabetes (GDM2) Trial is a single-center, parallel-arm, comparative effectiveness trial of one-step versus two-step GDM screening strategies on the rate of adverse perinatal outcomes including: large-for-gestational age (LGA) deliveries (primary outcome), small-for-gestational age (SGA), macrosomia, cesarean delivery, fetal growth and body composition, and maternal and neonatal composite outcomes. This paper describes the design and analysis plan of the GDM2 Trial as well as overall challenges in assessing the impact of screening and diagnosis strategy on adverse pregnancy outcomes. We will also assess whether the additional women diagnosed with the one-step approach benefit from treatment as assessed by metabolic profiles at one year postpartum. Ultimately, this study will provide the necessary evidence for establishing universal guidelines for GDM diagnosis and implementation into clinical care.