Associations between prenatal heatwave exposure and child development and behavior and the mediating role of maternal depression in Brazil

Background: Heatwaves are becoming more frequent and intense under climate change. Although prenatal heat exposure has been linked to adverse birth outcomes, its implications for early-childhood development and behavior remain poorly understood in tropical low- and middle-income settings. We examined whether prenatal heatwave exposure is associated with infant development and behavior, and whether current maternal depression mediates this association. Methods: We used data from the Brazilian Center for Early Child Development (CPAPI) birth cohort in Ribeirão Preto, São Paulo state, Brazil, comprising 946 infants born between July 2023 and March 2024. We assessed development and behavior at 6–10 months using the Survey of Well-being of Young Children and derived prenatal heatwave exposure from climate reanalysis data linked to maternal residential addresses. We estimated associations using a high-dimensional fixed-effects framework, adjusting for family, infant, and neighborhood characteristics, historical climate, and postnatal climate exposure, and decomposed these associations using a mediation analysis. Results: Prenatal heatwave exposure was not associated with developmental milestone scores. However, each additional heatwave day during pregnancy was associated with higher infant irritability, with a risk increase of approximately 13%. Prenatal exposure was also associated with increased maternal depressive symptoms, which accounted for 21%–22% of the associations with behavioral outcomes. Conclusion: Prenatal heatwave exposure was associated with early behavioral difficulties, suggesting that early behavioral regulation may be particularly sensitive to prenatal heat. Maternal mental health appears to be an important pathway, highlighting its relevance for climate adaptation and early-childhood health strategies.