[Effect of exogamy on morbidity among children during the first three years of life].

The incidence of common diseases among children in the first three years of life was studied in relation to the degree of outcrossing in family history, the level of education of both parents, and the age of entering nursery school. A total of 526 children (274 boys and 252 girls) were inspected. The factors under study proved to have no effect on morbidity among children under one year of age. However, morbidity during the second and third years of life depended on the degree of outcrossing in the children's family background, the educational level of their mothers, and the age of their entrance into nursery school. Higher morbidity at this age was characteristic of children born of parents belonging to different ethnic groups, and this situation was independent of social factors. The role of genetic coadaptation and epistasis in determining the relationship between outcrossing and morbidity is discussed.