Abstract
A growing body of epigenetic research suggests that in-utero adaptations to environmental changes display important sex-specific variation. We tested this heterogeneous adaptation hypothesis using data from 900 children born at the University Hospital in São Paulo, Brazil, between October 2013 and April 2014. Crude and adjusting linear models were used to quantify the associations between prematurity, being small for gestational age, and children's physical and mental development at 12 months of age. Prematurity was negatively associated with neuropsychological development in final models (z score difference, -0.42, 95% confidence intervals: -0.71, -0.14), but associations did not vary significantly by sex. For being small for gestational age, associations with height-for-age, weight-for-age, and neuropsychological development were also negative, but they were systematically larger for male than for female infants (P < 0.05 for all). These results suggest that male fetuses may be more vulnerable to intrauterine adversity than female fetuses. Further research will be needed to better understand the mechanisms underlying these sex-specific associations.