Oral Glucose Tolerance Test Response Phenotypes and Adverse Pregnancy Outcomes: A Secondary Analysis

Background: Gestational diabetes mellitus may present with different patterns of glucose abnormality during oral glucosetolerance testing (OGTT). These patterns may represent distinct glycemic phenotypes with different pregnancy risks. Thisstudy evaluated maternal and perinatal outcomes according to OGTT response phenotype. Materials and Methods: Thissecondary analysis included 100 pregnant women from a parent prospective observational study. Fasting, 1-hour and 2-hourOGTT glucose values were classified using cut-offs of 92, 180 and 153 mg/dL, respectively. Women were categorized asnormoglycemia, isolated post-load hyperglycemia or combined hyperglycemia. Maternal and perinatal outcomes werecompared between groups. Adjusted relative risks were calculated after adjustment for age, BMI and primigravida status.False discovery rate correction was applied for multiple outcome comparisons. Results: There were 34 women withnormoglycemia, 18 with isolated post-load hyperglycemia and 48 with combined hyperglycemia. Baseline characteristicswere comparable. Preterm delivery was highest in the isolated post-load group at 55.6% compared with 26.5% innormoglycemia and 20.8% in combined hyperglycemia (p=0.027). Core adverse pregnancy outcome occurred in 66.7%,29.4% and 33.3%, respectively (p=0.023). Perinatal composite outcome was also highest in isolated post-load hyperglycemiaat 72.2% (p=0.042). Compared with normoglycemia, isolated post-load hyperglycemia was associated with higher adjustedrisk of core adverse pregnancy outcome and perinatal composite. On direct comparison with combined hyperglycemia, theadjusted risk of preterm delivery was higher (aRR 2.60, 95% CI 1.31–5.14). None of the associations remained significantafter multiple-testing correction. Conclusion: Isolated post-load hyperglycemia showed a higher frequency of pretermdelivery and composite adverse pregnancy outcomes. These findings suggest possible clinical relevance of OGTT glycemicphenotypes but should be considered exploratory.