Ovarian reserve

Ovarian reserve is a term that is used to determine the capacity of the ovary to provides eggs that are capable of fertilization resulting in a healthy and successful pregnancy. The determination of the ovarian reserve is important in the treatment of infertility.

The ovary is generally thought of as an egg bank from which the woman draws during her reproductive life. While each month one egg is released by ovulation about one thousand additional eggs are lost by atresia. Few if any oocytes are replenished during the reproductive years. Thus with advanced maternal age the number of eggs that can be successfully recruited for a possible pregnancy declines. Attempts have been made to assess the number of potential useful oocytes in a noninvasive way.

The most commonly used test to assess this ovarian reserve is the day 3 FSH test. This blood test determines the level of FSH on cycle day 3. Cycle day 3 is chosen because at this time the estrogen level is expected to be low, a critical feature, as FSH levels are subject to a negative feedback. Thus any determination of FSH needs to include the corresponding estradiol level to indicate that the FSH level was drawn, when the estrogen level was low. In a patient with infrequent menstruation, an FSH level and estrogen level could be measured at random and is valid if the estrogen level is low. Generally FSH levels are expected to be below 10 miu/ml in women with reproductive potential (levels of 10-15 miu/ml are considered borderline). A clomiphene challenge test is a variation on this approach.

Another approach is to examine the ovaries by gynecologic ultrasonography and to determine their size as ovaries depleted of eggs tend to be smaller and to examine the number of antral follicles visible by sonography.

Women with poor ovarian reserve are unlikely to conceive with infertility therapy. Also see poor ovarian reserve for treatment options.