OBJECTIVE: Developmental defects of enamel (DDE) in preterm infants still require clarification and may favour dental caries, lower food intake, and greater difficulty with weight-height gain. We evaluated factors associated with DDE in preterm infants. SUBJECTS AND METHODS: In this prospective cohort study, we monitored 54 prematurely born infants from birth to 24 months of age. Trained and calibrated dentists examined the oral cavity of these children to identify and categorize DDE. Information on perinatal variables was collected from the infants' medical records and interviews with their mothers. The data were analysed using Student's t test, a chi-squared test, and Pearson's product moment correlation coefficient. RESULTS: A total of 46.3% of the 54 children presented DDE, which was observed more frequently in the left hemiarch in children born extremely (<28 weeks of gestation) or very preterm (28 to <32 weeks) (RR=2.2; 95% CI 1.3-3.6), with very low birth weight (<1500 g) (RR=2.0; 95% CI 1.1-3.5), who were admitted to the neonatal intensive care unit (RR=1.3; 95% CI 1.0-1.7), and who were intubated (RR=1.6; 95% CI 1.1-2.2). CONCLUSIONS: The high incidence of incisor enamel defects, particularly on the left side, was related to higher risk prematurity and to local trauma from intubation. This article is protected by copyright. All rights reserved.