Effortful control mediates associations of fetal growth with hyperactivity and behavioural problems in 7- to 9-year-old children.

BACKGROUND: Inverse associations of fetal growth with behavioural problems in childhood have been repeatedly reported, suggesting long-term effects of the prenatal developmental environment on behaviour later in life. However, no study so far has examined effects on temperament and potential developmental pathways. Temperamental traits may be particularly susceptible to neurodevelopmental alterations, and they are linked to behavioural problems. Therefore, we tested for associations of fetal growth with behavioural problems in children and tested if temperament mediated such effects. METHODS: One hundred and thirty-nine mother-child pairs were recruited in early pregnancy.Weight, head circumference and gestational age were measured at birth, and the mother reported on their child's behavioural problems and temperament at age 7 to 9 years. RESULTS: Birth weight and head circumference at birth adjusted for gestational age (i.e., fetal growth) were inversely associated with hyperactivity and total behavioural problems, and positively associated with the temperamental trait Effortful Control. Path analyses showed that Effortful Control mediated the effects of fetal growth on hyperactivity and total behavioural problems. CONCLUSIONS: Our results suggest that an adverse fetal environment is associated with behavioural problems in childhood, in particular in those children that show a low capacity for attentional and behavioural regulation. An adverse fetal environment might induce vulnerability for behavioural problems, or it might induce changes in temperament and behavioural problems independently, representing a common cause. Pathways are likely to be based on long-lasting neurodevelopmental alterations due to prenatal adversity.