Lab tests showing that women have low reserves of eggs in their ovaries may not necessarily mean they will struggle to get pregnant, a U.S. study suggests.
For the study, researchers examined results from blood and urine tests for so-called biomarkers that indicate ovarian reserve, or egg supply, in 750 women ages 30 to 44.
Women with test results indicating low ovarian reserve were no less likely to conceive within six or 12 months of attempts than women whose lab tests didn't point to a limited egg supply, researchers report in JAMA.
"These blood tests do predict how well a woman will respond to fertility treatment," said lead study author Dr. Anne Steiner of the University of North Carolina at Chapel Hill.
"However, we found that they do not predict her likelihood of conceiving naturally," Steiner said by email. "This challenges the clinical dogma that diminished ovarian reserve is a cause of infertility."
Women are born with a finite supply of eggs, and that supply dwindles with age. Tests for ovarian reserve biomarkers have become widely used as a growing number of women elect to put off attempting pregnancy until they're in their 30s and 40s.
Doctors use the tests to decide whether to recommend egg freezing as an option for women to preserve future fertility options, researchers note, and home-based tests are also marketed to women who want to assess fertility on their own.
The study examined tests of three biomarkers of ovarian reserve: early-follicular-phase serum antimullerian hormone (AMH), serum and urinary follicle-stimulating hormone (FSH) and serum inhibin B.
Women with lower levels of AMH and elevated FSH, which can point to limited egg supplies, weren't significantly less likely to get pregnant within 6 or 12 months of trying to conceive than women with normal test results, the study found.
Results from tests of inhibin B levels also weren't associated with fertility.
One limitation of the study is that it assessed conception, but not whether women successfully delivered babies, the authors note. Low ovarian reserve might increase the risk of miscarriage, potentially by impacting egg quality, researchers point out.
The study team also lacked data on the semen quality of women's male partners, making it impossible to determine how this might have influenced the odds of natural conception.
The study also evaluated the effectiveness of the tests in women who had been trying to conceive for up to three months, and many of these women might not have had any difficulty conceiving with a little more time.
Doctors typically advise women under 35 to get fertility assessments after 12 months of trying unsuccessfully to conceive and tell older women to get fertility checked out after six months of trying.
The best use of ovarian reserve tests is to determine which patients may respond to treatments that stimulate the ovaries to produce more mature eggs, said Dr. Nanette Santoro of the University of Colorado School of Medicine in Aurora. When ovarian reserves are too low, women may not benefit from fertility treatments.
Many women may not need these tests, or may not need to immediately act on the results, Santoro, author of an accompanying editorial, said by email.
"By the time you have come to a doctor for help getting pregnant, ovarian reserve is a large consideration," Santoro said. "But if you never need to see one of us, you could be walking around with very low ovarian reserve and still have no problem getting pregnant on your own if all other systems are 'go.'"