[Folliculogenesis in the prenatal period of human development]

Quantitative analysis of the follicular formation has been performed in ovaries of 97 human embryos and fetuses (6--40-week-old). The first oocytes at the stage of diplotene appear in 11.5--12-week-old fetuses. Primordial follicles are formed around the oocyte as early as the stage of diplotene. Follicles are intensively formed after the 14th--15th week. Single primordial follicles begin to transform into the growing primary ones in 17-week-old fetuses and the process becomes active after the 19th--20th week of the development. As a rule, the oocyte reaches the stage of dictyotene only after the follicle has transformed into the primary one. By the time of birth most of oocytes are enclosed by the primary, and in less number--by the primordial follicles. The number of secondary and tertiary cavitary follicles is small. The formation rate of follicles with binuclear oocytes and that of polyoocytic follicles is stated. The data on quantitative analysis of oocyte degeneration at the stages of diplotene and dictyotene are presented.