Diminished ovarian reserve facts
- Diminished ovarian reserve (DOR) describes a reproductive condition in which a woman has fewer eggs in her ovaries than other women of comparable age would.
- Diminished ovarian reserve can cause infertility in women or increased difficulty conceiving.
- Ovarian reserve testing comprises a variety of evaluations that helps a fertility specialist determine the quantity of a woman’s eggs in order to develop an infertility treatment plan.
- Even with diminished ovarian reserve, a woman can still conceive, especially through fertility treatments. These include ovarian stimulation, egg freezing (before egg quantity continues to decrease) and donor eggs.
- No tests are available to predict egg quality.
What is low ovarian reserve?
Ovarian reserve refers to the number of eggs (oocytes) that the ovaries contain. A diminished ovarian reserve, also called low ovarian reserve or low egg count, can be a factor in female fertility. A higher number and better quality of eggs significantly increase a woman’s potential to conceive.
Diminished ovarian reserve is defined as when a woman has fewer eggs than is expected for a woman of comparable age.
All women experience a natural decline in ovarian reserve due to aging. While the number and quality of eggs naturally diminish with a woman’s age, fertility varies significantly among women of similar age. As egg quantity decreases, the quality of eggs can also be lower than a similarly aged woman with normal ovarian reserve.
Aging ovaries and female infertility
A woman is born with all the eggs that she will ever have in her ovaries. As the quantity and quality of eggs decline through the childbearing years, the remaining eggs may not be as healthy, meaning the ability to conceive declines with age.
Ovarian reserve stats
- A female baby is born with approximately 2 million eggs.
- By puberty, that number drops to 300,000-500,000.
- At age 37, egg count decreases to approximately 25,000, although some women experience this decline earlier.
- By age 51, the number of eggs in a woman’s ovaries plummets to about 1,000.
A woman’s capacity to conceive decreases gradually but significantly beginning around age 32. By age 37, not only is there a severe decrease in oocyte number, but there is also a decrease in quality.
As a woman ages, the ratio of good quality eggs to abnormal eggs of poor quality shifts, with the poor quality eggs outnumbering the good ones. By menopause, all remaining eggs are of poor quality. These changes in egg quantity and quality affect conception success. In fact, aging ovaries are the factor most closely associated with female infertility.
Women under age 30 have approximately 20-25% chance of becoming pregnant with each menstrual cycle during the first year of attempting to conceive. After age 40, the chance of natural conception drops to less than 5% per cycle.
For women under 35, diminished ovarian reserve can signal premature ovarian failure, which is when the ovaries stop functioning before age 40 (see section below). DOR can significantly increase the risk of female infertility for women under 35.
What causes diminished ovarian reserve?
Aging of the ovaries is the general cause of DOR. More specifically, women with DOR were either born with fewer eggs than normal, lost them faster than other women typically do, or their eggs accumulated damage faster than normal. In many cases where DOR is diagnosed, the underlying cause can’t be determined.
The most common factor in a woman experiencing diminished ovarian reserve is being over the age of 35. Other factors that can contribute to diminished ovarian reserve include:
- Genetic issues, such as X chromosome abnormalities.
- Loss of an ovary.
- Surgery for ovarian cysts or tumors.
- Autoimmune disorders.
- Cancer treatments.
- Smoking/tobacco use.
According to the American Society for Reproductive Medicine (ASRM), diminished ovarian reserve has not been linked to any lifestyle behaviors except perhaps smoking.
Ovarian reserve testing
Ovarian reserve tests comprise blood tests to measure hormone levels and ultrasound imaging. These tests alone cannot diagnose diminished ovarian reserve, however. They provide a predictive value that a fertility specialist will weigh along with other factors, such as age and health history, to determine the best treatment for infertility.
Measuring AMH (anti-Müllerian hormone) levels is the new gold standard in assessing diminished ovarian reserve. AMH, which is produced by eggs in the ovaries, indicates how many eggs likely remain in a woman’s ovaries. As ovarian function declines, AMH production declines as well. AMH values greater than 1.0-1.2 are commonly accepted as normal.
Another test measures FSH (follicle-stimulating hormone), which is produced by the pituitary gland in the brain on day 3 of a woman’s menstrual cycle. As ovarian function declines, FSH production increases as a means to stimulate the ovaries to create eggs. Testing FSH levels on day 3 obtains the most accurate reading.
Most healthy women of childbearing age will have FSH values well below 10. A value of 10 in testing reflects a decline in ovarian reserve.
Ultrasound to measure follicle count
Transvaginal ultrasound allows a specialist to see and count a woman’s antral follicles (the egg-containing pockets in the ovaries) at the beginning of her menstrual cycle. Antral follicles foretell the potential number of retrievable eggs following ovarian stimulation, a protocol used in many fertility treatments.
Infertility treatments for diminished ovarian reserve
If a woman is diagnosed with DOR, it does not mean she cannot get pregnant. It does mean however, that it may be more difficult and may require fertility treatment.
Time is of the essence with diminished ovarian reserve because the earlier the diagnosis, the better the chances of conception, especially with the woman’s own eggs. The older a woman is the likelihood of a needing to take a more aggressive approach increases.
Ovarian stimulation alone does not always help patients with low ovarian reserve. But there are certain treatments that can increase the odds of conceiving. If DOR is diagnosed early enough, it may be possible for a patient to freeze her eggs for future fertility.
Premature ovarian aging vs. menopause
According to the National Institutes of Health, an estimated 10% of women might be at risk of premature ovarian aging (POA), a cause for diminished ovarian reserve. This condition should not be confused with perimenopause or menopause.
Perimenopause is a period of years around the mid-40s when the female body is in transition. In perimenopause, the body continues to produce estrogen, and ovulation still occurs.
However, during perimenopause the ovaries are aging and slowing their production of female hormones. The pituitary gland releases higher and higher levels of FSH to push the ovaries to act normally, but it gets harder and harder for the ovaries to create normal levels of estrogen.
Menopause is the resolution of perimenopause. On average, it comes around the age of 51. Menopause is typically diagnosed once a woman shows elevated signs of FSH and has not had a period in at least 12 months, meaning ovulation has completely stopped. Once a woman goes through menopause, there is no chance of getting pregnant on her own.