Early Pregnancy Glycemic Testing for Prediction of Gestational Diabetes and Large for Gestational Age Birthweight

Objective: We evaluated if early pregnancy oral glucose tolerance testing (OGTT) or continuous glucose monitoring (CGM) improves gestational diabetes (GDM) or large-for-gestational-age birth (LGA) prediction over clinical factors alone. Research Design and Methods: In Glycemic Observation and Metabolic Outcomes in Mothers and Offspring (GO MOMs), a prospective observational study at nine US sites (2021-2025), participants with singleton gestation and without pre-existing diabetes underwent blinded 75-gram OGTT and CGM at 10-14 weeks’ gestation. Predictive models for GDM at 24-28 weeks’ and LGA were developed using these data and clinical factors (maternal age, body mass index, GDM or macrosomia history). New glycemic criteria maximized area under ROC curve in training data from four sites and were validated in five. Models incorporating OGTT or CGM criteria vs. clinical factors alone compared PPV at prespecified NPV at reported 8.3% national GDM prevalence and 10% for LGA. Results: Of 2178 participants, 93.3% who were pregnant at 24-28 weeks completed OGTTs (15.4% GDM) and 98.1% with live births had data to determine LGA (11.2% LGA). At NPV ≥96% and 8.3% GDM prevalence, PPV for GDM was 12.2% (11.0%-13.3%) for clinical factors alone, 26.5% (23.1%-30.3%) for OGTT plus clinical factors, and 19.8% (17.2%-22.5%) for CGM plus clinical factors. For LGA, neither glycemic model improved PPV. Validation confirmed findings. Conclusions: In a US-representative population, adding 10-14 week OGTT or CGM criteria to clinical factors improved GDM but not LGA prediction. Future studies should determine if predicting GDM in first trimester facilitates interventions that improve GDM-related pregnancy outcomes.