Background: The objective of this study was to determine whether there was an association between mothers' light drinking during pregnancy and risk of behavioural problems, and cognitive deficits in their children at age 3 years.
Methods: Data from the first two sweeps of the nationally representative prospective UK Millennium Cohort study were used. Drinking patterns during pregnancy and behavioural and cognitive outcomes were assessed during interviews and home visits. Behavioural problems were indicated by scores falling above defined clinically relevant cut-offs on the parent-report version of the Strengths and Difficulties Questionnaire (SDQ). Cognitive ability was assessed using the naming vocabulary subscale from the British Ability Scale (BAS) and the Bracken School Readiness Assessment (BSRA).
Results: There was a J-shaped relationship between mothers drinking during pregnancy and the likelihood of high scores (above the cut-off) on the total difficulties scale of the SDQ and the conduct problems, hyperactivity and emotional symptom SDQ subscales. Children born to light drinkers were less likely to score above the cut-offs compared with children of abstinent mothers. Children born to heavy drinkers were more likely to score above the cut-offs compared with children of abstinent mothers. Boys born to mothers who had up to 1-2 drinks per week or per occasion were less likely to have conduct problems (OR 0.59, 95% CI 0.45-0.77) and hyperactivity (OR 0.71, 95% CI 0.54-0.94). These effects remained in fully adjusted models. Girls were less likely to have emotional symptoms (OR 0.72, 95% CI 0.51-1.01) and peer problems (OR 0.68, 95% CI 0.52-0.92) compared with those born to abstainers. These effects were attenuated in fully adjusted models. Boys born to light drinkers had higher cognitive ability test scores [standard deviations, (95% CI)] BAS 0.15 (0.08-0.23) BSRA 0.24 (0.16-0.32) compared with boys born to abstainers. The difference for BAS was attenuated on adjustment for socio-economic factors, whilst the difference for BSRA remained statistically significant.
Conclusions: Children born to mothers who drank up to 1-2 drinks per week or per occasion during pregnancy were not at increased risk of clinically relevant behavioural difficulties or cognitive deficits compared with children of abstinent mothers. Heavy drinking during pregnancy appears to be associated with behavioural problems and cognitive deficits in offspring at age 3 years whereas light drinking does not.