Intrafamilial incidence of autism, cerebral palsy, and mongolism.

A comparative study of developmentally disturbed children as well as normal children is presented with a focus on their position in the family. Demographic data were compared for three groups of Japanese children, with a mean age of 4 years 7 months, who were diagnosed as autistic, cerebral palsied, and trisomic (trisomy 21 mongoloid). The areas compared were maternal age at birth, ratio of males to females, number of siblings, birth order, and age interval between the subject and the closest younger sibling. The normal kindergarten children with a mean age of 4 years 6 months, as well as the Japanese general population, were also compared for these demographic items. The findings on maternal age and sex ratio for these three nosological groups are consistent with recent studies. Although the reproduction of mothers of either cerebral palsied or mongoloid children ceases after the birth of the propositi, the reproduction of mothers of autistic children does not show significant difference from that of normal children's mothers. The age intervals between the subjects and the closest younger sibling do not differ among the three groups or in the normal group.