AMH or anti-mullerian hormone is a hormone produced by the viable follicles (which contain eggs) that remain in the ovary. It is an excellent indicator of ovarian reserve. Young women with large numbers of healthy eggs tend to have high AMH levels whereas older women or women with a low number of healthy eggs will have lower levels of AMH.  New information is suggesting that very high levels of AMH may not simply indicate a plethora of antral follicles, but may indicate a follicular dysfunction.
AMH levels do not fluctuate very much throughout the cycle and are not impacted by the levels of other hormones such as estrogen or progesterone.
Abnormal AMH levels are usually determined by comparing a woman’s own AMH level with that of a large group of women her own age who do not have infertility. For example, an AMH of 1.4 would be considered very low for a fertile 18-year-old but would be considered average for a 36-year-old.
Fertility decreases with age. This decrease is most likely due to aging of the eggs and the chromosomes inside them. The risk of miscarriage and chromosomal abnormalities in babies also increase with age. The most successful method for achieving a pregnancy and taking home a baby at advanced female age is with the use of egg donation.