Mental retardation in urban children: a population study of reduced optimality in the pre-, peri- and neonatal periods.

One hundred and thirty representative cases of mentally retarded children in Sweden were surveyed in order to detect reductions in optimality in the prenatal, perinatal and postnatal periods. There was a small but statistically significant reduction in optimality, particularly pertaining to the prenatal and neonatal periods. It is of interest, however, that these mentally retarded children had smaller reductions of optimality than did children with cerebral palsy or infantile autism.