How they work: The U.K. test and also some U.S. fertility-clinic tests measure levels of Anti-Müllerian hormone (AMH) and other substances called inhibin B and follicle-stimulating hormone (FSH), which are present when egg-producing follicles are growing. Higher hormone levels suggest more fertility. Another test uses ultrasound to count the follicles with developing eggs. And the most common test measures FSH along with one form of estrogen. These tests, individually or in combination, may be able to tell if your ovaries are functioning normally.
Experts say: All this science has some flaws. Knowing that your ovaries are still working isn’t the same as knowing how many viable eggs you haveor predicting the future. Even positive results don’t mean you can count on a big window. At the same time, negative results don’t mean you’re out of luck.
“These tests can’t tell you the prognosis a year from now,” says Marcelle Cedars, MD, director of the reproductive endocrinology division at the University of California, San Francisco. “I’d hate to see people make important life decisions based on the results.”
Bottom line: Ultimately, age is still the most important factor when it comes to fertility prediction, says Mark Perloe, MD, medical director of Georgia Reproductive Specialists in Atlanta. If you’re in your early 40s, the odds are against getting pregnant without help, no matter what the tests say. The odds are much better in your late 30s or younger. In short, the tests may be encouraging or discouraging, but they cannot accurately determine how much time you’ve got left for motherhood.