As more women are delaying childbirth and more baby boomers are reaching midlife, the problem of diminished ovarian reserve (DOR) is increasing. This has several major medical consequences including infertility, decreased bone mass with risk of fracture, abnormal uterine bleeding from lack of regular ovulation, and hot flashes.
A woman is born with her entire life supply of eggs, approximately 1-2 million. At the time of her first menstrual period, the number of eggs has diminished to 300,000-400,000. Each cycle, hundreds of eggs will begin to grow but usually only one is released during ovulation; the others are reabsorbed and disappear from the ovaries.
Peak fertility in women occurs before age 30, with a monthly pregnancy rate of 20-25 percent. This monthly rate starts to decrease around age 32, but rapidly declines beginning in the late 30’s and into the 40’s. Approximately one in three women experience infertility by age 40, mainly due to poor egg quality. Egg quality decreases as a woman ages, resulting in impaired fertilization, reduced implantation, and increased risk of miscarriage along with the increased potential for chromosomal abnormalities of the fetus. Although we expect the ovary to age in a specific way, the rate at which oocytes are lost is not something that can be controlled and varies among individuals, based on a woman’s genetic makeup.
Ovarian reserve screening is an essential tool in the initial evaluation of patients experiencing infertility, especially those who are over thirty-five. Several measures exist for testing a woman’s ovarian reserve. Dr. Gehlbach prefers to determine an antral follicle count while he performs a transvaginal ultrasound. The number of small (antral) follicles within the ovary correlates with the total number of eggs within the ovary. Most ovaries with a normal complement of eggs will have 4 or more antral follicles at any given time.
If the antral follicle count appears to be low, Dr. Gehlbach may order a blood test on the third day of your menstrual cycle to measure FSH (Follicle Stimulating Hormone) and Estradiol levels. These hormones are another way to evaluate ovarian reserve. Estradiol should be less than 50 and FSH should be less than 10 to be considered within normal limits. If the FSH and/or Estradiol are elevated, these results could indicate decreased ovarian reserve. Although FSH and estradiol levels can fluctuate from month to month, a single elevation is often predictive of poor ovarian function.
Another way to evaluate ovarian reserve is to measure an antimullerian hormone level. This hormone is produced by the early growing (antral) follicles and correlates with the number of eggs within the ovary. It can be drawn anytime during the menstrual cycle. It is a relatively new test and there is some disagreement about what constitutes a normal level, but extremely low levels are also consistent with diminished ovarian reserve.
Women with diminished ovarian reserve may still conceive, but their pregnancy chances are lower than those with normal ovarian function. Their ovaries often do not respond well to stimulation with fertility drugs, and some are not able to undergo in vitro fertilization for this reason. In severe cases, the use of an egg donor may be required.
For More Information from ASRM on Diminished Ovarian Reserve and Infertility