Relationship Between Early-Pregnancy Glycemia and Adverse Outcomes: Findings From the TOBOGM Study

OBJECTIVE: We evaluated associations between early-pregnancy oral glucose tolerance test (OGTT) glucose and complications in the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) cohort to inform prognostic OGTT thresholds. RESEARCH DESIGN AND METHODS: Individuals with risk factors for hyperglycemia were recruited for an international, multicenter, randomized controlled gestational diabetes mellitus (GDM) (World Health Organization 2013 criteria) treatment trial. A 2-h 75-g OGTT was performed at <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, and high band). RESULTS: Overall, 3,645 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 values, there were continuous positive associations with late GDM: adjusted odds ratio (aOR) 2.04 (95% 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, birth weight ≥4,500 g, respiratory distress, phototherapy requirement, stillbirth/neonatal death, and shoulder dystocia), with aOR 1.15 (95% CI 1.04-1.26) and 1.14 (1.04-1.25), respectively, and with large-for-gestational-age offspring, with aOR 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 (≥10.6 mmol/L [191 mg/dL]) predicted the perinatal composite. CONCLUSIONS: 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.