At 23Plus we want you to be educated on all thing’s fertility. A common test which you may have heard of measures AMH levels, the test is also known as “the egg timer test.” It has become increasingly popular in the last few years globally. While AMH testing is often marketed as a test than can help women work out how much time they have left to have children, this is not a proven use. In fact, a number of studies have shown there is no evidence that AMH levels can predict a woman's chances of becoming pregnant naturally. AMH levels will tell you the quantity of a woman’s eggs, but it won't tell them how long they've got to have children. AMH testing tells a woman nothing about the quality of her eggs, and it only takes one "golden" egg to be fertilised to produce an embryo.

https://www.abc.net.au/news/science/2018-09-23/what-is-an-egg-timer-test-for-fertility-and-does-it-work/10234086