The distribution of the number of pregnancies, births and abortions in the Kharkov population was analysed in the cohort of women with the completed fertility. The mean number of pregnancies per woman was 3.77 for the first generation and 4.30 for the second generation. The mean number of births in the first and second generations was 1.47 and 1.35. The Crow's Index of the opportunity for selection and its components connected with differential mortality was estimated. The value of the Crow's Index was decreased during one generation from 0.56 to 0.35. In the women of the second generations having high and secondary education, the number of pregnancies was 3.72 and 4.38, respectively, the Crow's Indexes being 0.33 and 0.35.