Relationship between early pregnancy glycemia and adverse outcomes: Findings from the TOBOGM Study

Objective We evaluated associations between early pregnancy OGTT glucose and complications in the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) cohort to inform prognostic OGTT thresholds. Research Design & Methods Individuals with risk factors for hyperglycemia were recruited for an international, multicenter randomized controlled GDM (WHO 2013 criteria) treatment trial. A 2-h 75-g OGTT was performed <20 weeks’ gestation. Individuals with early treated hyperglycemia in pregnancy were excluded from the primary analysis. Early OGTT glucose concentrations were analyzed continuously and in glycemic categories (normal, low band, high band). Results Overall, 3645 individuals had an OGTT at (mean±SD) 15.6±2.5 weeks. For each 1 SD increase in fasting, 1-h and 2-h glucose there were continuous positive associations with late GDM: adjusted odds ratios (aORs) 2.04 (95% Confidence Interval [CI] 1.82-2.27), 3.05 (2.72-3.43) and 2.21 (1.99-2.45), respectively. There were continuous positive associations between 1-h and 2-h glucose and the perinatal composite (birth <37+0 weeks, birth trauma, birthweight ≥4500g, respiratory distress, phototherapy requirement, stillbirth/neonatal death, shoulder dystocia): aORs 1.15 (95%CI 1.04-1.26) and 1.14 (1.04-1.25), and with large-for-gestational-age: aORs 1.18 (1.06-1.31) and 1.26 (1.01-1.25), respectively. Significant associations were also observed between 1-h glucose and cesarean section and between fasting and 2-h glucose and neonatal hypoglycemia. In categorical analysis, only the high band 1-h glucose (≥10.6mmol/L [191mg/dl]) predicted the perinatal composite. Conclusion There is a continuous positive association between early pregnancy OGTT glucose and complications. In individuals with hyperglycemia risk factors, only the high glycemic band 1-h glucose corresponded to increased risk of major perinatal complications.