Obstetric complications and mild to moderate intellectual disability.

BACKGROUND Mild to moderate intellectual disability affects 2.5% of the general population and is associated with an increased risk of several psychiatric disorders. Most cases are of unknown aetiology although genetic factors have an important role. AIMS To investigate the role of obstetric and neonatal complications in the aetiology of mild to moderate intellectual disability. METHOD Obstetric and neonatal complications recorded at the time of pregnancy and delivery were compared between participants with mild to moderate intellectual disability, age-matched siblings and unrelated controls using logistic regression. RESULTS Admission to a special care baby unit and not being breastfed on discharge were more common in people with mild to moderate intellectual disability. Not being breastfed on discharge was also more common in those with intellectual disability than unaffected siblings. Foetal distress was more common among controls than among those with mild to moderate intellectual disability. CONCLUSIONS Admission to a special care baby unit and not being breastfed on discharge may be related to the aetiology of intellectual disability, although the direction of this association is unclear.