[Factors associated infant development in Brazilian children: baseline of the impact assessment of the Happy Child Program].

The study aimed to assess socioeconomic, family, and individual factors associated with infant development (i.e., in the first year of life) among families with social vulnerability. This was a cross-sectional analysis of baseline data from a randomized trial. The study included 3,242 children < 12 months of age living in 30 municipalities from five regions of Brazil. The choice of states and municipalities was intentional, based on the implementation of the Brazilian Happy Child Program. The sample was selected among eligible children for the Brazilian Happy Child Program, and the objective was the promotion of infant development. The Ages and Stages Questionnaire (ASQ) was used to assess infant development. A three-level analytical model (state, municipality, and individuals), using the Wald test for heterogeneity and linear trend, estimated the mean ASQ-3 and 95% confidence interval (95%CI). The analyses were adjusted for potential confounders. Information was analyzed for 3,061 (94.4%) children with available data for ASQ-3. Infant development scores (total and in all the domains) were some 12% lower in preterm children and those with intrauterine growth restriction (small for gestational age). Lower scores were seen in children of mothers with low schooling, depressive symptoms, two or more children under seven years of age living in the household, and who did not report self-perceived support or help during the pregnancy. In conclusion, potentially modifiable characteristics (schooling, maternal depression, and prematurity/intrauterine growth restriction) showed greater impact on reducing the infant development score in all the target domains.