The changing epidemiology of cerebral palsy.
AIM: To determine the prevalence of cerebral palsy in a specific population. METHODS: Multiple sources of ascertainment were used to create and maintain a register of all cases of cerebral palsy born to mothers resident in the counties of Merseyside and Cheshire in the years 1966 to 1989. Denominator data of infant births and deaths from 1966 to 1981 were obtained from statutory notifications made to health authorities and, for the period 1982-89, from statutory birth and death registrations. Over 1500 cases formed the database for the study. RESULTS: The prevalence of cerebral palsy has increased among all the low birthweight groups with, most recently, an increase in infants weighing < 1000 g at birth. Low birthweight infants now comprise about 50% of all cases of cerebral palsy; in the early years of the study they comprised about 32% of all cases. The proportion of cerebral palsy by clinical type has changed among low birthweight babies, with relatively fewer cases with diplegia and a concomitant increase in the proportion with hemiplegia. An increase in the severity of functional disability, determined by the proportion of children with severe learning, manual, and ambulatory disabilities, was also found. CONCLUSIONS: The change in the epidemiology of cerebral palsy has implications for the aetiology of the condition, and for health, educational, and social service provision.