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These Two Fertility Tests May Not Be Accurate

Tests that estimate ovarian reserves failed to predict who got pregnant in a new study.

Olivia Campbell

Kelly Knox/Stocksy

So you're thinking about starting a family—maybe you're pushing 30 and wondering if you've left it too late or if you might be able to wait a few more years. For many women, the next order of business would be to take a fertility test, either at home or at their doctor's office. These tests typically measure the levels of follicle-stimulating hormone (FSH) present in the urine; some fertility clinics may offer tests for antimüllerian hormone (AMH).

How can these hormones give us hints about fertility exactly? First you need to know that women are born with all their eggs and as a woman gets older, the number of eggs available for fertilization declines. As a woman's egg supply shrinks, the granulosa cells in her ovaries produce less AMH and less inhibin B, a protein that blocks the production of the other hormone people test for, FSH. With less inhibin B, FSH levels can increase, so having high FSH is thought to indicate fewer eggs. Collectively, AMH, FSH, and inhibin B are known as biomarkers of ovarian reserve. It's like the Federal Reserve, but for eggs.

The assumption is that how many eggs a woman has can predict her chances of actually getting pregnant. So a fertility test showing high FSH levels might lead someone to start trying for a baby or freeze her eggs ASAP because she thinks she's running out of time. Meanwhile, a test showing low FSH levels might result in people confidently hopping back on birth control for a few more years.

Well, a new study suggest that taking action based on these test results may be unwise. After collecting data from 750 women ages 30 to 44 attempting to conceive naturally, researchers found that those with biomarkers indicating low ovarian reserves were just as likely to get pregnant after six or 12 menstrual cycles as those with normal ovarian reserves. And that's after adjusting for age, weight, race, smoking status, and recent hormonal contraceptive use. The finding means that ovarian reserve may not actually say much about fertility when trying to conceive through sex.

The authors concluded: "These findings do not support the use of urinary or blood FSH tests or AMH levels to assess natural fertility for women with these characteristics."

"The quality of the egg appears to be more important than the quantity," says Anne Steiner, lead study author and an assistant professor of reproductive endocrinology and infertility at the University of North Carolina School of Medicine. "One side of this is that we want to reassure, not cause false anxiety, in women whose tests show diminished ovarian reserve. The opposite is true, too: we don't want women being falsely reassured by good values on tests."

Use of these tests by the general population grew out of their use in fertility clinics. "These biomarkers do correlate with the number of eggs in the ovary, and can predict response to fertility treatment [like IVF]. We would check these values when women came in, and if nothing else came up except low egg count, we presumed that was the cause of the infertility," Steiner said. "It was assumed they would also predict a woman's ability to conceive."

The study recruited women who'd been trying to conceive for less than three months and followed them for up to menstrual 12 cycle attempts at pregnancy. It's important to note that the researchers only looked at data from women who had not been diagnosed with a condition that affects fertility, such as polycystic ovary syndrome or endometriosis. In those cases, biomarkers of ovarian reserve may be crucial in helping their fertility specialist determine a course of treatment. But studies of whether they can predict pregnancy rates following fertility treatment have proven inconclusive.

So if these tests aren't a Magic 8 Ball for a woman's chances of getting pregnant, what is? "Her age," Steiner says, but acknowledging: "No one wants to hear that." Women who are still ovulating (not in perimenopause or beyond) and having regular menstrual cycles can assume some level of fertility.

"There's no test," Steiner says, but there's also "not a magic age that we turn into a pumpkin." After age 35, there are some subtle dips in fertility, then after 37 they tend to get bigger, and then can be quite big after 40. "The difference between age 30 and 33 is not going to be very big; the difference between 36 and 39—that's very impactful."

One caveat is that the pregnancies were not followed beyond the first few weeks, so it's uncertain if the miscarriage rates differed among the two groups. Steiner says they are looking at the miscarriage data right now and will present their findings at the American Society for Reproductive Medicine meeting at the end of the month.

In an editorial accompanying the study, Nanette Santoro, the chair of obstetrics and gynecology at the University of Colorado School of Medicine, writes that the assumption has been that "a lower-than-normal number of remaining ovarian follicles may suggest a lower likelihood of future fertility." But that these results mean "it may be necessary to reevaluate what an AMH level really means for a woman's reproductive health." Santoro was not involved in the study.

According to Santoro, who "women who have never attempted to conceive should not be evaluated in a manner similar to those with infertility. Doing so can not only provide potentially misleading and anxiety-producing results but may also lead to costly fertility preservation treatments that have no value." So skip the drugstore tests, everyone.

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