HINT: It's not a crystal ball
Anti-mullerian hormone (AMH) is a serum (or blood) marker for ovarian reserve. It’s a hormone that is secreted by the developing follicles and gives us insight into how many follicles are recruited each cycle (this can also be measured directly via ultrasound - called antral follicle count)
AMH typically peaks around 20-25 y/o and naturally declines with age. The average yearly decrease in AMH value was 0.2ng/mL/year through age 35 and then 0.1 ng/mL/year after age 35. It’s important to note that these are averages and we don’t know how quickly it will decline in for each individual.
These are the ‘normal ranges’ for AMH based on age:
NOTE: These ranges are in pmol/L, the other commonly used metric is ng/mL (you can do the conversion here: https://unitslab.com/node/155)
For a long time, we have associated low AMH with poor fertility outcomes. And it has been used as a surrogate marker for predicted future fertility. We don’t have much research to support this, and future fertility is not guaranteed with a normal AMH level.
But what if you have low AMH for your age, what does that mean?
Great question…
Serum AMH levels have poor predictive value for natural pregnancy. Meaning a low AMH doesn’t mean you can’t conceive naturally. It actually doesn’t say anything about your ability to conceive naturally!
If we look at the graphical representations below, they show the stratification of high, normal and low ovarian reserve (measured with AMH and antral follicle count) and compared it to pregnancy rates.
Source: Nelson, Fertil Steril, 2013
Source: Zarek. JCEM 2015
RESULTS: Over 3, 6, 9 and 12 months women with low AMH are as likely to get pregnant as those with normal or high levels. This is true for both older (>35) and younger (<35) women who are trying to conceive. Again, AMH is NOT a predictor of your ability to achieve a natural conception.
What about IVF?
This is where AMH is useful, AMH is an excellent predictor of how well the ovaries respond to stimulation medication in IVF cycles. A low AMH typically results in a poorer response in women to controlled ovarian stimulation, resulting in fewer eggs and pregnancies than in women of a similar age. The inverse is true, a high AMH (most commonly seen in PCOS), puts women at higher risk for ovarian hyperstimulation syndrome (OHSS).
The Bottom Line: low AMH levels cannot predict the chances of conceiving naturally or give us valuable information about your future fertility but they do predict a poorer response to IVF stimulation medication.
The Take Away: Don’t get disheartened by a low serum AMH value, continue to try to conceive naturally while taking steps to improve egg quality and rule out underlying reasons for a lower AMH that may be contributing to your increased time to conception (auto-immunity, toxic exposures, etc.).