Fetal growth and behaviour problems in early adolescence: findings from the Mater University Study of Pregnancy

The nature of the association between birth weight and behavioural problems in adolescence is unclear. Recent studies are limited by their capacity to adjust for important obstetric and measurement issues. Aim To examine the nature of the association between birth weight and a range of behavioural symptoms, including anxiety/depression and social problems, in adolescence.

Data from 4971 mothers and their children participating in the Mater University Study of Pregnancy (MUSP), a prospective, population-based birth cohort, are presented. This study commenced in Brisbane, Australia, in 1981. Mothers and their children were followed up at 3-5 days post-birth, and 6 months, 5 years and 14 years after the initial interview. Internalizing and externalizing behaviour problems, social problems and anxiety/depressive symptoms were assessed using Achenbach's Youth Self Report (YSR) of the Child Behaviour Check List (CBCL).

There was no evidence of a linear association between birth weight and behavioural symptoms, when birth weight z-scores were examined as a continuous variable. However, a non-linear association was identified when birth weight z-scores were categorized into quintiles. Children in the lowest and highest quintiles were at higher risk of increased anxiety/depressive and social problems symptoms. After adjustment for potential confounders, birth weight showed a non-linear association with the log odds of social problems {Quintile 1 odds ratio (OR) 1.59 [95% confidence interval (CI) 1.13, 2.23] Quintile 5 OR 1.57 (95% CI 1.12, 2.20)}.

Our findings provide further support for an association between birth weight and some adolescent behaviour problems. This association is likely to be non-linear, affecting babies at both the lower and higher ends of the birth weight distribution.