A woman’s ovaries will hold hundreds of thousands to millions of eggs at birth. Throughout a woman’s lifetime, only about 300-400 of those eggs will become mature and be released for fertilization. When a girl reaches puberty, her egg count will have diminished to around 400,000. By reaching menopause, she will only have about 400-500 eggs.
The large supplies of eggs within each ovary are immature, or primordial, and must undergo growth and maturation each month. The eggs are stored within follicles in the ovary. Within a woman’s lifespan, large numbers of follicles and oocytes will be recruited to begin the growth and maturation process. The large majority, however, will not reach full maturity. Most will die off in a process called atresia. Thus, only about 300-500 of these eggs will mature over a women’s life span.