Diminished Ovarian Reserve

Diminished ovarian reserve overview

  • Diminished ovarian reserve means that a woman’s ovaries have fewer eggs remaining than is normal for her age or that the eggs are of poor quality.
  • Women are born with all the eggs they will ever have, which is called their ovarian reserve.
  • With age, the number of those eggs diminishes naturally, from 1-2 million at birth to about 25,000 at around the age of 37.
  • Having low quality and a limited number of eggs in the ovaries can make getting pregnant difficult or result in female infertility.
  • Some causes of diminished ovarian reserve include fewer eggs than normal at birth, the faster than normal loss of eggs, increased damage to the eggs, an autoimmune disease affecting the eggs or genetic makeup.
  • We evaluate ovarian reserve in order to predict a woman’s prospects for getting pregnant or the chances of success with fertility treatments like in vitro fertilization (IVF).

How many eggs does a woman have?

Women’s bodies contain all the eggs (oocytes) they will ever have when they are born. The number of those eggs never increases, it only decreases.

The American College of Obstetricians and Gynecologists reports that on average, a woman has 6-7 million eggs as a fetus; 1-2 million eggs at birth; 300,000-500,000 at puberty; about 25,000 at age 37; and only 1,000 at age 51.

The rate at which this reserve diminishes rapidly increases at around age 32 and declines even faster after age 37. This is thought to be the primary way in which age affects fertility in women.

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What is diminished ovarian reserve?

Ovarian reserve is the predicted number of eggs a woman has in her ovaries, as well as the quality of those eggs. High-quality eggs are more likely to result in a successful pregnancy. A diminished ovarian reserve (DOR) means the woman has fewer eggs than expected for her age.

A woman’s ovarian reserve is what people are actually referring to when they talk about the female “biological clock.” With increasing age, the chances of a successful pregnancy decrease: her fertility clock, so to speak, is running out of time.

The production of good eggs for fertilization is an essential process of female fertility. DOR, with either fewer eggs or eggs of poor quality, makes conception difficult or results in female infertility.

Deterioration of ovarian reserve varies from woman to woman, with young women usually experiencing this less frequently. Because of the differences in women regarding egg loss, evaluating ovarian reserve is an important tool in understanding problems a couple has getting pregnant.

Strict guidelines for defining DOR do not exist and determining what is an average number of eggs for a woman is difficult. This is partly due to individual differences. How we measure ovarian reserve, which is primarily done by observing hormone levels and not an actual count of the eggs, is also a factor.

What causes this reduction in women’s eggs?

A woman loses eggs every day, even before she is born. Egg loss accelerates considerably after around age 32, depending on the individual. DOR generally shows up around menopause, but can take place earlier. A woman still loses eggs when she is pregnant, when she is on birth control or when she has abnormal menstrual cycles.

As a woman ages, her eggs and the cells around them become damaged, a hallmark of DOR along with reduced total number. The ratio of damaged eggs to normal ones increases with age. When a woman ovulates a faulty egg it will be more difficult for her to become pregnant, if not impossible, than it would be if she had ovulated a healthy egg.

A damaged egg that is fertilized by sperm is also more likely to result in miscarriage. A baby born from a damaged egg has an increased likelihood of birth defects.

In many instances of DOR, fertility specialists can’t identify the reason for the abnormal number or quality of eggs. However, the three primary causes of diminished ovarian reserve are believed to be:

  • Being born with a less than normal number of eggs.
  • Losing eggs at a faster rate than is normal for a woman’s age.
  • Experiencing greater cumulative damage to eggs over time.

Aside from the above causes, other risk factors can increase the chance of a woman having DOR. These include: genetic problems with the X chromosome, smoking, forms of ovarian surgery, fertility damaging medical treatments such as chemotherapy, pelvic infections and tubal disease.

Female fertility tests for diminished ovarian reserve

Most often there are no symptoms of poor ovarian reserve. Problems getting pregnant are one sign, and some women with DOR have shorter menstrual cycles.

We usually discover DOR when evaluating a woman or couple for infertility. Measuring reproductive hormones is one method of identifying diminished egg supply. Transvaginal ultrasound is another, which helps us count the ovaries’ antral follicles.

DOR testing can enable our fertility specialist to predict if a woman has fewer healthy eggs in reserve than is normal, and thus a greater chance of having difficulty conceiving. This testing is most effective in evaluating a woman’s chance of pregnancy through in vitro fertilization (IVF).

It is important for patients to know that a test showing even considerable diminished ovarian reserve does not mean the individual can’t get pregnant naturally.

Antral follicle count

A follicle is a group of cells that contain an egg and nurture it. Mature follicles have fluid around them that shows up on transvaginal ultrasound. As part of a fertility evaluation, we measure how many mature follicles a woman has during her menstrual cycle. A large number of follicles signals that the ovary has an appropriate level of eggs. If less than 10 follicles are on the two ovaries (combined), this qualifies as DOR.

Follicle-stimulating hormone & estradiol testing

The follicle-stimulating hormone (FSH) is involved in egg production. We conduct a blood test to evaluate FSH levels on the second or third day of a woman’s menstrual cycle. If the level is high compared with those of women the same age without DOR, it means the woman has a lower chance of having a live birth. This is the case even if we use ovulation induction with IVF as a method to increase her likelihood of getting pregnant. We often test for levels of estradiol, a form of estrogen related to FSH, at the same time.

Anti-Müllerian hormone (AMH)

When follicles emerge from storage in the ovary, they release the anti-Müllerian hormone (AMH). Higher levels of AMH indicate a higher number of follicles coming out of storage. This is an accurate means of predicting that there are enough eggs that can grow during IVF. Low levels of AMH are indications of DOR. This test is often done at the same time as the FSH test.

Assisted reproductive technologies to work around DOR

DOR cannot be slowed or prevented. But women with poor ovarian reserve can still get pregnant with assisted reproductive technologies. These include the following.

Fertility preservation through egg freezing can be tried as soon as DOR is diagnosed. Women who suspect they may have ovarian reserve issues and wish to preserve their fertility should freeze their eggs when they are young and their reserve is better. They can then use these eggs through IVF when they are ready to become pregnant.

Using donor eggs with IVF, a woman with DOR can achieve pregnancy. Her partner’s sperm can fertilize the eggs, and the embryo can be implanted in her uterus. The child will have the male partner’s genes but not the genes of the birth mother.

Superovulation, an enhanced form of ovulation induction, is another option. Hormones cause the woman to ovulate several eggs, which can be used in a fresh IVF cycle or cryopreserved for future IVF.