Maternal hyperglycaemia in pregnancy represents the most common medical condition complicating both the antenatal and postnatal periods. Despite this there is still much controversy surrounding neonatal complications and postnatal management designed to avoid them. Even with advances in perinatal care, newborns of mothers with hyperglycaemia in pregnancy remain at risk for a multitude of physiologic, metabolic, and congenital complications. While postnatal hypoglycaemia occurs in up to 15 % of normal newborn babies in early postnatal life, the incidence in babies who have risk factors is much greater: up to 50 % in infants of diabetic mothers, large and small babies and 66 % in preterm babies. Care of these infants has focused on ensuring adequate cardiorespiratory adaptation at birth, possible birth injuries, and maintenance of normal glucose metabolism. Critically, neonatal hypoglycaemia is the only neonatal morbidity independently associated with later developmental delay in late preterm babies. While it is uncertain what degree or duration of hypoglycaemia is necessary before morbidity occurs, it is known that even babies without symptoms can have adverse outcomes. Here, the controversies which remain over the implications for the baby of differing approaches to maternal hyperglycaemia management will be discussed. In addition, the significant knowledge gaps in the data supporting current approaches to treatment of neonatal hypoglycaemia, despite repeated calls for the development of evidence-based treatment guidelines, will be highlighted.