Background: Early life experiences have important consequences on health and human capital throughout life. The development is the result of interaction between the child's biological characteristics and cultural and social factors on which it is inserted. Biological factors that cause developmental delay associated with environmental factors increase the chance of the infant having an inappropriate development. This shows the importance of studies assessing factors related to child development. Objective: The aim was to characterize the neurological development of children 6-8 months ago through the Bayley scale in a population-based sample, then estimate the prevalence of delay and identifying psychosocial and environmental risk factors. Method: A longitudinal epidemiological study of birth cohort study in a group of 368 infants and their mothers. Two moments of assessment were considered: a) at the beginning of the third trimester of gestation and b) when the infants were 6-8 months of age. The study aims to examine the neurological development of the children considered for the study through the Bayley scale, to estimate the prevalence of delay in a population-based sample and, finally, to identifying maternal psychosocial and environmental risk factors. Results: Indicated that maternal stress factors (i.e. anxiety and substance disorder during pregnancy, lower maternal schooling and economic class) were associated with lower cognitive development in infants. Conclusion: This study shows the importance of screening to identify possible developmental delays, for subsequent intervention programs to prevent or minimize future hazards and allow the child to develop to their full potential.