The epidemiology and causes of cerebral palsy.

Cerebral palsy is the commonest physical disability in childhood, occurring in 2.0 to 2.5 per 1000 live births. Although the total number of children with cerebral palsy has remained stable or increased slightly since 1970, there has been a consistent rise in the proportion of cerebral palsy associated with preterm and very preterm births. Known causes of cerebral palsy--whether prenatal, perinatal or postnatal--must be distinguished from risk factors or associations. Much is known about such risk factors which, alone or in combination, may indirectly result in cerebral palsy. Causes and risk factors implicated in cerebral palsy are discussed in detail, together with directions for future research.