Women are born with a finite number of eggs in their ovaries and menopause occurs when they are finished. Approximately 10 years prior to menopause conceiving becomes more difficult as more than 70% of the remaining eggs are genetically abnormal. This also explains why older women abort more frequently. It is estimated that approximately 90% of the pregnancies in women older than 45 end up in a miscarriage.

Ovarian reserve is the major determinant of pregnancy in couples who are trying to conceive on their own as well as couples undergoing infertility treatment. The success of IVF largely depends on the ovarian reserve as women with good reserve produce more eggs and eventually end up with more embryos that can be transferred and subsequently frozen and stored. Ovarian reserve can be determined by checking the levels of FSH and estradiol on the 2^nd or 3^rd day of the menstrual cycle.

Vaginal ultrasonography performed during the same period also allows a quite precise estimation of the ovarian reserve by counting the antral follicles (tiny cysts which carry eggs inside) that can respond to stimulation by the drugs used for IVF.

The capacity of the ovaries has to be very carefully evaluated especially in women with a family history of early menopause, who previously had a cyst removed from their ovaries, women with a single ovary, women with history of endometriosis, infertility with no obvious cause in young couples, and in couples with repeated miscarriages. In women with diminished ovarian reserve proceeding to IVF without any further delay is necessary. The efficacy of alternative treatments such as ovulation induction with out without intrauterine insemination is minimal and is usually considered a waste of time.