[Incidence rates of cerebral palsy, mental retardation and Down syndrome in Sodegaura City, Chiba Prefecture].

For the purpose of early detection and early habilitation for developmentally handicapped children, we started medical screening in 1978 for pediatric neurological diseases among children in Sodegaura City, Chiba Prefecture with a total population of about 50,000. A statistical analysis were performed for the incidence of cerebral palsy (CP), mental retardation (MR, I.Q < 70) and Down syndrome (Down). The number of liveborn babies during 1978-1987 was 5,070. The number of patients with CP, MR and Down were 11, 44 and 5 respectively. The incidence rates of CP, MR and Down were 0.217%, 0.868% and 0.099% respectively, which were almost equal to those recent reports. The rate of perinatal brain damage with CP was 81.8%. The incidence rates of mild MR (MMR, I.Q 69-50) and severe MR (SMR, I.Q < 50) were 0.512% and 0.355% respectively. The SMR rate was almost equal to recent reports, and the MMR rate was different from some reports. The rates of prenatal brain damage, perinatal brain damage, postneonatal brain damage and unknown origin with MR were 20.5%, 22.7%, 4.5% and 34.1% respectively. The rate of perinatal disorders, which play some role in the etiology of MR, was 18.2%. Even now, the perinatal disorders play a major role of CP and MR. Therefore the progress of perinatal medicine is strongly desired.