Cerebral ventricular enlargement and reduced cortical volume are correlates of chronic schizophrenia. We investigated whether genetic risk for psychosis related to differences in foetal brain development as measured by prenatal ultrasonography. Routine foetal cerebral measures at 19-23 weeks of gestation were compared between the offspring of 35 women with a history of psychosis and 105 control women matched for gestational age. Overall, no significant differences were found between the high-risk and control groups. There was a non-significant trend in the adjusted analysis towards increased lateral ventricular width in the offspring of mothers with psychosis.