An epidemiological study of disability in 4-year-old children from a birth cohort in Frederiksborg County, Denmark.

In an epidemiological study of a county cohort of 4,138 liveborn children, surveyed at age four, 45 had disability (1.1%). The following period prevalences from birth to age four in per mille were found: motor handicap 5.1, to include cerebral palsy 4.1, myelomeningocele and hydrocephalus 0.5, and metabolic disorders 0.5; severe mental retardation 2.9, mild 1.4, subnormality 2.7; epilepsy 4.6; severe visual defect 1.4; severe auditory defect 0.7. Perinatal damage alone was likely in only three children out of 45. Two thirds had a prenatal cause or a combination of prenatal and perinatal causes. Birth asphyxia seemed to be a rare cause of motor disability and mental retardation. Prematurity per se gave a risk of spastic diplegia, but not of mental retardation. Among the mentally retarded, half were light for gestational age, and in more than half, the damage occurred prenatally.