[Rural family with many children at the end of the 20th century]

A prospective study of 3 cohorts of rural families (with 10-year interval) was carried out for the first time. The first cohort included 79 families with many children, observed for 30 years since 1970; the 1980 cohort (observed for 20 years) consisted of 37 families, and the 1990 cohort (observed for 10 years) consisted of 23 families with many children. Analysis of the reproductive function of cohorts of families showed changes in the number of children in the families: the percentage of families with many children and the mean number of children in a family decreased. Causes essential for the structure of a family with children and birth rate decrease are analyzed.