A baby girl is born with 1 to 2 million oocytes (human eggs) in her ovaries. When she hits puberty all but about 300,000 will have died before becoming mature eggs. Of these, 300 to 400 will be ovulated during a woman’s reproductive lifetime. By menopause all of the eggs are gone. A baby girl is born with every egg she will ever shed, and more.
Poor ovarian reserve (low fertility):
Poor ovarian reserve is a condition of low fertility characterized by 1): low numbers of remaining eggs in the ovaries or 2) impaired egg development and recruitment.
Women with poor ovarian reserve have a lower chance of becoming pregnant than women with normal ovarian reserve in their same age group. Age is the main factor associated with poor ovarian reserve. Egg count and egg quality both decrease with age, causing women to become less likely to become pregnant and more likely to have miscarriages as they get older. These changes are most noted as a woman reaches her mid-to-late 30s.
Aside from age, risk factors for poor ovarian reserve include: Genetic factors (eg. fragile x syndrome), Adrenal gland impairment, Autoimmune disorders, radiation, chemotherapy, some forms of surgery (eg. laserization of the surface of the ovary to treat endometriosis), smoking, early menarche (starting menstruation at an early age), and having a family history of premature menopause. Some young women have diminished ovarian reserve even if they have no known risk factors.