Abstract
Data on 570 mothers and their children whose development was personally assessed from birth to four years were analysed. Strong associations were found between the incidence of fetal distress during labour, birth asphyxia, and delivery by emergency caesarean section. At the age of four years girls and children in the non-manual social classes were more advanced, developmentally, than boys and children in the manual classes. No associations were found between perinatal factors and total developmental scores; but highly significant differences were found between `at risk' pregnancy groups according to their method of developmental scores. In only one of seven handicapped children could the handicap possibly have been attributable to delivery factors. Case histories of two children illustrate the dangers and difficulties of associating cause and effect in individual patients.