We women are accustomed to peeing on chemically-treated sticks to learn what our bodies are up to. Pregnancy tests administered in the confines of the master bathroom are more accurate than ever, but new research indicates that home fertility tests can’t be relied upon. A quarter of women were labeled infertile by the tests, according to a study conducted by researchers at the University of North Carolina at Chapel Hill, although in actuality they had no more trouble getting pregnant than other study participants. (More on Time.com: 5 Pregnancy Taboos Explained (or Debunked))
Home fertility tests are gaining in popularity as women increasingly delay baby-making. Some haven’t found the right guy; others are sailing ahead in their careers. When they decide the time is right for baby, more than a few are turning to home fertility tests to assess their chances. Inaccurate assessments of infertility could lead otherwise healthy women to seek unnecessary fertility interventions.
“The best fertility test we have right now is age,” says lead study author Anne Steiner, an assistant professor of obstetrics and gynecology at UNC. “Age we know is a great way to tell you your probability of getting pregnant naturally.”
The over-the-counter fertility tests that Steiner studied measure follicle-stimulating hormone (FSH), which can help predict the timing of menopause and the likelihood of conceiving following fertility treatments, though it’s not clear if FSH levels can forecast natural fertility in the general population. It’s possible that the FSH thresholds for infertility used in the tests need to be adjusted, says Steiner. “So it may be that this test can pinpoint infertility, but we need to uniquely define where that cutoff is going to be,” says Steiner. (More on Time.com: Photos: Pregnant Belly Art)
It’s also likely that a more accurate fertility test could be developed to incorporate anti-Mullerian hormone (AMH) — which indicates egg supply — instead of FSH. The “sister hormone” to FSH, AMH can’t be detected in the urine; a blood test is the only way and even that has yet to be approved for clinical use.
Steiner and colleagues presented their research this week at the annual meeting of the American Society for Reproductive Medicine in Denver. They studied 100 women at risk of reproductive aging, an inevitable process defined as being between the ages of 30 (yikes!) and 45. Once the women ceased birth control, researchers began to measure levels of three hormones: estrogen, FSH and AMH. They adjusted for intercourse patterns and observed whether the hormone levels predicted how long it took each women to get pregnant. According to the parameters of drug-store fertility tests, 25% of the women had abnormal FSH levels that would correlate with infertility. Yet after tracking the women for six months, researchers found they had no more difficulty getting pregnant than women deemed fertile. Increasing the tests’ FSH threshold levels, however, did result in a correlation with infertility, indicating the tests’ validity leaves something to be desired. (More on Time.com: Building a Brighter Kid: Consider IVF)
“The question is what is the value of these tests,” says Steiner. “I’d say it needs further investigation. I don’t think they’ve been appropriately evaluated.”
In short, it might be better to save your pennies for an AMH test, which some fertility clinics perform — instead of shelling out for a drugstore fertility test.