There is no single test that will tell us that a woman will or will not get pregnant
It is well known that a woman’s fertility or the potential to get pregnant decreases as she ages. As a woman gets older she has fewer eggs and poorer quality to the eggs that are present. This results in both a decrease in pregnancy rates and an increase in miscarriage rates.
While all women have decreasing fertility as they age, the extent varies from woman to woman. A woman’s “ovarian reserve” or fertility potential can be evaluated with various tests. It is important to realize, however, that these tests only give us a better idea of the woman’s fertility potential. There is no test that will tell us that a woman will get pregnant or will not get pregnant.
Ovarian reserve can be evaluated with the following testing methods.
Baseline hormone levels
FSH is a hormone made by the pituitary gland to stimulate egg development in the ovary. Levels are typically low at the beginning of the menstrual cycle and then vary across the cycle. As the ovary ages, more FSH is required to initiate the stimulation of the ovary.
Elevated FSH levels at the beginning of the cycle are associated with a lower chance of pregnancy with any fertility treatment. Estrogen levels are evaluated along with FSH. Estrogen should be low at the beginning of the cycle, because if it is elevated it can artificially lower the FSH values. So if there is a normal FSH but high estrogen level, this can also suggest poor chance of pregnancy.
Baseline testing is typically done on day 3 of the cycle, as this is when FSH and estrogen should be at their lowest, although testing can be done from day 2-4. The presence of an ovarian cyst may make the hormone results inaccurate. If they are abnormal, they should be repeated after the cyst has resolved.
Antimüllerian hormone (AMH)
AMH is a hormone made directly in the ovary by the follicles that surround developing eggs. AMH levels have minimal variation across the menstrual cycle, so the test is not cycle-day specific. AMH levels may vary from lab to lab, so your doctor needs to know what is normal for a particular lab. As AMH levels drop, chance of pregnancy diminishes.
Antral follicle count
The small resting follicles that surround developing eggs can be seen on ultrasound. Counting these small follicles gives an indication of fertility potential and likely response to fertility medications. The follicle count also helps determine appropriate dose of fertility medication. Antral follicle count is most accurate if done at the beginning of the cycle and performed by a provider experienced with fertility ultrasound evaluations.
Other less common methods of testing ovarian reserve are sometimes used. One example is the clomiphene citrate challenge test. FSH and estrogen are measured both at baseline and after taking clomiphene citrate. It is not clear if this gives any additional information beyond baseline hormonal testing.
Ovarian potential can also be gauged by previous response to fertility medications. If high doses of gonadotropins are required to stimulate the ovaries, this suggests a decreased ovarian response and may be associated with a decreased pregnancy rate.
While results may vary from cycle to cycle, chance of pregnancy tends to go along with the most abnormal results. Unless there is a situation known to affect reserve testing, such as an ovarian cyst or recent ovarian or fallopian tube surgery, there is little justification to do repetitive testing in subsequent months.
Normal reserve testing suggests a better chance of pregnancy for that age. Normal test results do not change the fact that fertility gets worse as a woman ages.
Older women with abnormal ovarian reserve testing have a definite decreased chance of pregnancy. For these women, donor eggs or embryos may be the best option for fertility.