The low birth rate in the world, especially in developed countries, causes an increase in the old age rate in countries and as a result, many economic and social problems. In the study, a number of economic, social, educational and other factors affecting the birth rate in countries were examined on the basis of resources and statistics in the relevant field. The relationship between the birth rate and factors such as the development level of the countries, the education level of women and the proportion of women among employees was analyzed by the fuzzy inference method. The accuracy of fuzzy inference rules was tested by performing Naive Bayes classification on the dataset.