Early‐ vs. late‐onset gestational diabetes: Differential impact on maternal and neonatal outcomes

INTRODUCTION: The timing of gestational diabetes mellitus (GDM) diagnosis may influence maternal and neonatal outcomes, yet the differential impact of early-onset versus late-onset GDM remains incompletely characterized, particularly in Chinese populations. To compare maternal and neonatal outcomes between early-onset GDM (diagnosed before 20 weeks' gestation) and late-onset GDM (diagnosed at 24-28 weeks' gestation). MATERIAL AND METHODS: This retrospective cohort study included 1847 singleton pregnancies complicated by GDM at Qingdao Municipal Hospital from January 2020 to December 2023. Participants were classified into early-onset (n = 583) and late-onset (n = 1264) groups. Primary outcomes included composite adverse neonatal outcome, preeclampsia, and cesarean delivery. Multivariate logistic regression was performed to calculate adjusted odds ratios (aOR) after controlling for maternal age, pre-pregnancy BMI, nulliparity, family history of diabetes, and chronic hypertension. RESULTS: Women with early-onset GDM demonstrated significantly higher rates of insulin requirement (45.8% vs. 21.1%, p < 0.001). Early-onset GDM was associated with increased risks of preeclampsia (aOR 1.85, 95% CI 1.38-2.47), cesarean delivery (aOR 1.84, 95% CI 1.53-2.28), and preterm birth (aOR 2.69, 95% CI 2.05-3.47). Neonatal complications were substantially elevated in the early-onset group, including macrosomia (aOR 1.86, 95% CI 1.41-2.37), neonatal hypoglycemia (aOR 2.04, 95% CI 1.57-2.67), respiratory distress (aOR 2.60, 95% CI 1.78-3.71), and NICU admission (aOR 2.16, 95% CI 1.69-2.74). The composite adverse neonatal outcome occurred in 61.2% of early-onset versus 37.7% of late-onset cases (aOR 2.57, 95% CI 2.13-3.15). CONCLUSIONS: Early-onset GDM may represent a clinically distinct, higher-risk phenotype with notably elevated maternal and neonatal morbidity compared to late-onset disease. Given the observational design and the potential for residual confounding, these findings should be regarded as hypothesis-generating rather than definitive. They require confirmation in prospective, multicenter studies before risk stratification by diagnostic timing or intensified surveillance can be advocated for routine clinical implementation.