All women have a finite number of eggs in their body which, when released during ovulation, can be fertilized to produce a baby. Most people believe that all that matters when you are trying to get pregnant is the number of eggs you have – if you have a lot of eggs, you’ll get pregnant. Unfortunately, this is not the case. True, the number of eggs that you have does matter, but so does the quality of those eggs. Together, the number and quality of your eggs are referred to as your ovarian reserve. Ovarian reserve testing is done to assess a women’s ability to produce eggs that will ultimately produce a baby. Therefore tests to determine a woman’s fertility are often called ovarian reserve testing.
Age is the most important determinant of ovarian reserve, Egg quality is greatly affected by your age. In your 20s and early 30s, you should have a large number of good quality eggs. But, women in their 20’s and 30’s will have a few bad eggs too. As you age your eggs will begin to decline in quality as well as in number. By the time you are in your late 30s or early 40s, you will have more poor quality eggs than good quality eggs. That is why fertility declines as one ages.
Having poor quality eggs is a common reason for infertility. The decline in egg quality and quantity can sometimes be explained based on a woman’s medical history but in some women there is not a clear reason why the egg quality is poor. Decline in ovarian reserve, and therefore egg quality, can occur due to pelvic surgery, endometriosis, smoking, cancer treatments, or family history of early menopause. To assess a woman’s ability to achieve a pregnancy, doctors will conduct an evaluation of her ovarian reserve using tests that measure egg quantity and quality.
The evaluation process typically begins with a blood test to measure the naturally-occurring hormones FSH (follicle stimulating hormone), estradiol and AMH (anti-mullerian hormone). These hormones are typically measured on cycle day 2, 3, or 4. The AMH level is the most important of these three tests, and is the best predictor of success with fertility therapy.
Anti-Mullerian hormone is a substance produced by granulosa cells in ovarian follicles. The granulosa cells surround each and every egg in a woman’s ovary. Therefore, the more eggs, the more granulosa cells, and the higher the AMH – Therefore AMH helps predict egg quantity. Of course the more eggs there are, the better chance there are good quality ones to help a woman achieve pregnancy.
A follicle-stimulating hormone (FSH) levels on the third day of the menstrual cycle is also a predictor of ovarian reserve. Women who have an increased FSH level will have a lower chance of achieving pregnancy with fertility therapy. Over the last 20 years, fertility centers have noticed that women with elevated FSH levels have decreased egg quality, and women with very elevated FSH levels rarely conceive using their own eggs. FSH is typically used to evaluate egg quality.
Another test used to measure ovarian reserve is the antral follicle count. The doctor uses a vaginal ultrasound to visualize the ovaries and to count the number of small “antral” follicles in the ovaries. A low number of follicles indicates a lower chance of conception and pregnancy. Typically an AFC above 10 is considered “okay” but a count above 15 is a better predictor of success.
It is important to recognize that a poor result from ovarian reserve testing does not signify an absolute inability to conceive and should not be the sole criteria considered to limit or deny access to infertility treatment. Ovarian reserve testing should be used to identify those individuals that may have a poor response to ovarian stimulation with fertility medications and a lower probability of achieving a live birth from fertility therapy. The ovarian reserve tests should be used to help a patient decide if a treatment is worth proceeding with based on cost and chance of success.