The article presents the results of the analysis of the dynamics of the age profile of the female population of fertile age and identifies the factors affecting the fertility rates. It is shown that the absolute number of the female population living in the southern territories of the Irkutsk region has decreased. The proportion of the cohort of fertile age women has decreased in general in the population of the total population and in the population of the female population. The reduction in the number of women of fertile age has led to a change in their age structure towards its aging, a decrease in the proportion of young, active reproductive ages. Special fertility rates make it possible to obtain a quantitative characteristic of the intensity of childbirth. Over the 23-year study period, the fertility rates of the female population have increased in general. It was revealed that in the dynamics, maximum fertility has moved to older age groups (25-29 years), characterizing the intensifying demographic processes of the implementation of "late motherhood". As a result of applying the index analysis method, it was revealed that in most southern territories of the region such as: Irkutsk, Angarsk, Angarsk district, Shelekhov, Usolye, Usolsky district, Cheremkhovo, Cheremkhovsky district. in the dynamics of 2005-2023. a decrease in the index of the number of births was recorded. On average, by territory, the key factor influencing the decrease in this index was a decrease in the index of the proportion of women of childbearing age in the total number of women. By territory, the contribution of factors to the decrease in the index of the number of births was different. Thus, for such territories as: Irkutsk, Cheremkhovo, Cheremkhovsky district, Usolye, Angarsk, the key factor in decreasing the index of the number of births was a decrease in the index of the proportion of women of childbearing age from all women. For territories such as: Angarsk and Usolsky districts, the factor determining the decrease in the index of the number of births was a decrease in the fertility rate of the female population. In the Irkutsk and Shelekhovsky districts, a positive trend in the increase in the birth rate index has been formed. The leading factor in the increase in the birth rate index in the Irkutsk district is the increase in the index of the proportion of women of fertile age from all women. For the Shelekhovsky district, this is an increase in the average population index. Calculated special coefficients allow us to predict the dynamics of population reproduction in individual territories and are an important link in the development of regional programs for strengthening the demographic potential of the territories of the constituent entity of the Federation.

special fertility coefficients of the female population, age structure of the female population, index model of fertility, contribution of factors to fertility.