Objectives The aim of this paper is to evaluate the prevalence of enamel defects in infants from a socially and economically poor population and the possible association of these defects with disturbances occurring in the pre-, peri- and postnatal periods of human development. Participants 117 infants aged between 16 and 18 months old were included in four groups based on gestational age and whether part or full term pregnancy. Method The data were collected in two stages: hospital-based, where gestational and birth records were examined, and home-based, where dental examinations and nutrition were evaluated. The teeth were cleaned and dried with gauze and examined in the open air, avoding direct sunlight in the knee-to-knee position. The enamel defects were coded according to the modified Developmental Defects of Enamel Index. Besides this, body weight and height were considered as anthropometric measures for the evaluation of nutritional status by the National Center for Health Statistics standards. Main outcome measures The data were analyzed using the chi-square and Fisher Exact tests. Besides these tests, logistic regression models were used. Results The prevalence of enamel defects was 49.6%, higher in the group of male infants (p<0.001). The most frequent type of defect and the most affected surface were, respectively, diffuse opacity (9.5%) and the buccal surface (83.3%), located in the gingival half (6.7%). The logistic regression model showed that educational level, gestational age and intrauterine growth retardation (IUGR), besides a lack of breastfeeding, increased the probability of enamel defects up to level of 5%. Conclusions The association between enamel defects and the etiologic factors shown in this study suggest the existence of social influences regarding oral health and teeth development. Key words: Enamel defects; etiology, primary, incisors