The intensity of births in the study population of women, who are of childbearing age.

Female fertility rate is calculated as the ratio of the number of live births and the number of women in the reproductive age (15—49). Besides total rate, age-specific fertility rates are published, that are calculated as the ratios of the number of live births from women and the number of these women in the same groups of age. Births from mothers in the age under 15 are counted to the group 15—19 and from the mothers in the age of 50 and over — to the group 45—49.