Trends in cohort fertility of the Dariusleut Hutterite population.

A church book containing vital information on Dariusleut Hutterite families enabled us to trace the life course of individual women. We conducted a retrospective cohort study on the women born in the Dariusleut sect for the period 1901-1965, focusing on their marriage and reproductive histories. The subjects were grouped into 5-year birth cohorts from 1901-1905 to 1961-1965. The marital age-specific fertility rate (MASFR) increased from the 1901-1905 cohort to the 1926-1930 cohort and then began to decrease, particularly at the ages of 30-39 years. The initial increase in MASFR was not reflected directly in the cohort mean of the total number of children per woman because of a concurrent delay in age at marriage. Marriage delay, however, could not explain the drastic decrease, which started in the 1931-35 cohort, in the total number of children per woman; the decrease in MASFR at the ages of 30 years and older was considered a major reason for the recent changes in Hutterite fertility. The causes of the recent fertility decrease of Hutterites at higher ages remain to be investigated.