Gestational diabetes mellitus (GDM) is one of the most common endocrinopathies during pregnancy. The issue on the prevalence of its adverse outcomes depending on the time of diabetes onset – before or during pregnancy – is still remaining unclear. The aim of this study was to determine the prevalence and risk of adverse outcomes associated with GDM in neonates in Poltava region. Materials and methods. We conducted a retrospective study that included 10.025 infants born to primigravidae under 28 weeks. Group I included infants (n = 35) who were born to mothers with GDM, and group II covered infants (n = 82) who were born to mothers with pre-gestational diabetes mellitus (PGDM). The control group included 9908 infants who were born to mothers without diabetes. Results. The risks of neonatal respiratory distress were significantly higher in neonates born to women with PGDM and GDM than in women without diabetes (RR 59.6 (95% CI 39.9-88.9) and RR 81.7 (95% CI 38.1- 175), whereas the risk of asphyxia was higher only in women with GDM (RR 16.4 (95% CI 6.5-41.4). Among the mothers with PGDM and GDM, no significant differences were observed in the number of infants with macrosomia (51.4% and 61.0%), hypoglycemia (37.1% and 31.7%), hospitalization in the intensive care unit (31.4% and 48.8%) and mechanical ventilation (20.0% and 23.2%). Conclusion. Diabetes mellitus is associated with an increased risk of developing maternal and neonatal adverse outcomes. The incidence of preeclampsia, premature birth, neonatal respiratory distress, macrosomia, and the use of mechanical ventilation in infants are the same in mothers with gestational and pre-gestational diabetes mellitus.