Prenatal influences on childhood psychological development

The intrauterine period is a sensitive phase for later disease susceptibility, and could affect common expressions of poor psychological development such as internalising and externalising problem behaviours, temperament or social competence. In this thesis, the associations between birth weight, maternal weight and maternal dietary factors in pregnancy, respectively, and these childhood psychological traits were examined in four European birth cohorts of twins or singletons. Children of women with pre-pregnancy overweight/obesity who gained 0.5kg/week during gestation had up-to 25-point higher average problem behaviours (on a 0-100 scale) compared to children whose mothers gained 0.2kg/week. Additionally, highest vs. lowest maternal Mediterranean-diet score was associated with a 16.3% average reduction in the probability of externalising behaviours, while no association was observed for internalising problems. By contrast, controlling for shared genetic and environmental influences, a greater intrapair birth-weight difference in monozygotic (identical) twins was associated with higher internalising symptoms in co-twins with lower compared to larger birth weight. Little-to-no evidence was found for the associations between maternal polyunsaturated fatty acids or pre-pregnancy weight and childhood outcomes. Nonetheless, further research is warranted to strengthen the evidence by addressing the influence of genetics and other parental lifestyle factors.