Third trimester abnormal oral glucose tolerance test and adverse perinatal outcome

Objective: To compare perinatal outcome of women after third trimester oral glucose tolerance test (GTT) following normal glucose challenge test (GCT) stratified by test results. Study design: Retrospective cohort study of women delivered in a tertiary, university affiliated medical center (2007–2012). Inclusion criteria were women with a normal 50 g GCT (<140 mg/dl) followed by GTT, who delivered a live-born fetus >28 gestational weeks. Gestational diabetes mellitus (GDM) was defined as ≥2 pathological values on GTT (Carpenter and Coustan’s criteria). Perinatal outcome was stratified by GTT results: normal (if all 4 values were normal), single pathological value or GDM. Logistic regression analysis was utilized to adjust outcomes to potential confounders. Results: Overall, 323 women met inclusion criteria. Of them, 277 (85.8%) had 4 normal values, 32 (9.9%) had a single pathological value and 14 (4.3%) had late-onset GDM. Infants of mothers diagnosed and treated as GDM had lower birth weights, compared to non-diabetics and those with a single pathological value GTT. Mothers with GTT ≥1 pathological values had statistically insignificant higher rates of cesarean delivery. However, this difference was not significant after adjustment to potential confounders. Conclusion: Treatment of late-onset GDM may lead to lower birthweights, presumably due to glucose control. No association was found with cesarean delivery or neonatal outcome.