ABSTRACTAimTo elucidate risk factors associated with adverse perinatal outcomes in early‐gestational diabetes mellitus (GDM).Materials and MethodsA dataset of 385 early‐GDM cases from a prospective cohort was analyzed. Early‐GDM was diagnosed if one or more of the following criteria were met: fasting plasma glucose (PG) levels of 92–125 mg/dL, 1‐h PG levels ≥180 mg/dL, and 2‐h PG levels ≥153 mg/dL during a 75‐g oral glucose tolerance test before 20 weeks of gestation. Multivariate analysis was used to examine associations between candidate risk factors and a composite outcome of maternal and neonatal adverse events.ResultsPre‐pregnancy overweight/obesity (pre‐pregnancy body mass index [BMI] ≥25.0 kg/m2) was significantly associated with a higher risk of the composite outcome compared with normal weight (pre‐pregnancy BMI of 18.5–24.9 kg/m2), an adjusted risk ratio (aRR) of 1.44 (95% confidence interval [CI]: 1.08–1.93), and an adjusted risk difference (aRD) of 13.6% (95% CI: 2.6–24.6%). Compared with fasting PG levels below 92 mg/dL, levels between 95 and 125 mg/dL were associated with a significantly higher risk of the composite outcome, with an aRR and aRD of 1.42 (95% CI: 1.01–1.99) and 12.9% (95% CI: 0.3–25.5%), respectively.ConclusionsEarly‐GDM, combined with pre‐pregnancy overweight/obesity and/or fasting PG levels of 95–125 mg/dL, is associated with a higher risk of adverse perinatal outcomes and should be prioritized for intervention.