To describe the clinical outcome of infants born to mothers with gestational diabetes mellitus (GDM) and preexisting insulin-dependent diabetes mellitus (IDDM).Setting: A tertiary care regional perinatal center with a specialized diabetes-in-pregnancy program.Design: Case series.Results: Five hundred thirty infants were born to 332 women with GDM and 177 women with IDDM. Thirty-six percent of these 530 newborns were large for gestational age, 62% were appropriate for gestational age, and only 2% were small for gestational age. Seventy-six (14%) of all infants were born before 34 weeks' gestation, 115 (22%) between 34 and 37 weeks of gestation, and 339 (64%) at term. Two hundred thirty-three infants (47%) were admitted to the neonatal intensive care unit due to respiratory distress syndrome(RDS),prematurity,hypoglycemia,orcongenitalmalformation. Hypoglycemia (more common among infants of maternal diabetic classes C through D-R) was documented in 137 (27%) of all newborns. One hundred eighty-two infants (34%) had RDS of varying severity. Polycythemia (5% of infants), hyperbilirubinemia (25%), and hypocalcemia (4%) were other morbidities present. Two hundred fortyfour infants were admitted for routine care and enteral feedings. Forty-three of these newborns required subsequent transfer to the neonatal intensive care unit for treatment of hypoglycemia (16 cases), RDS (19 cases), or both (8 cases). Routine care failures were more common among infants whose mothers had advanced diabetes, but less frequent among breast-fed infants.Conclusions: With modern management, fewer morbidities can be expected in infants of diabetic mothers. Those infants born to women with IDDM remain at risk for hypoglycemia, which can be treated in one half of the cases by enteral feedings alone. The majority of cases of RDS are mild and require short admissions to special care nurseries. Optimal care of infants of diabetic mothers is based on prevention, early recognition, and treatment of common conditions.Severecongenitalmalformations,significantprematurity,RDS,recurrenthypoglycemicepisodes,andasymptomatic infants of women with advanced IDDM should be admitted to special care nurseries. Breast-feeding among women with GDM and IDDM should be encouraged.