Ovarian reserve refers to the number of eggs that women have at an exact moment in time. All women are born with a finite number of eggs of approximately 1-2 million, although the fetus at 20 weeks gestation has 6-7 million eggs. As a woman ages, the number of eggs available decreases. Thus, a woman has about 300,000 eggs at puberty.
Finally, when a woman reaches menopause, the number of eggs will be depleted and she will have no ovarian reserve.