According to clinical studies, infants of diabetic mothers (IDM) seem to run a higher risk of mineralization disturbances in the enamel than normal healthy infants. In order to evaluate this observation at the histologic level, exfoliated primary incisors were collected from 74 IDM, representing two types of care during gestation and the perinatal period, and from 52 healthy children.The width of the neonatal line was evaluated in the enamel and the dentin by study of bucco-lingual undemineralized sections. Pre-and postnatal enamel was classified according to discolorations, deviations of prisms and hypoplasia. Microradiographic studies included measurements of the neonatal lines and classification of the degree of mineralization in the pre-and postnatal dental hard tissues.Irrespective of treatment, the IDM showed a significantly higher incidence of widened neonatal lines and also an increased frequency of postnatal disturbances compared to the controls. The observations are discussed against the background of the neonatal hypocalcemia reported in IDM.