(AP) -- Doctors could one day use a blood test to predict decades in advance when women will go into menopause, scientists say.
In research to be presented on Monday at a European fertility conference in Rome, Iranian experts say their preliminary study could be a first step toward developing a tool to help women decide when they want to have children.
The test does not predict when women will lose their fertility - which typically occurs about a decade before menopause - but if doctors know when women will go into menopause, they can calculate roughly when they will run out of eggs. Scientists say the test could be especially helpful in identifying women who might go into menopause early - in their late 40s or earlier instead of their mid-50s.
At the moment, there are few clues for doctors to tell which young women may be headed for early menopause. Blood tests and ovary scans only give women a few years' advance notice.
Iranian scientists took blood samples from 266 women aged 20 to 40 and measured the amount of anti-Mullerian Hormone, or AMH, in their bodies. Testing the amount of AMH in women tells doctors how many eggs there are left in the ovaries. Two more blood samples were taken in the following six years and physical exams were also performed.
Based on the amount of AMH women had, scientists used a mathematical model to estimate when women would go into menopause. Of the 63 women in the study who have hit menopause, the researchers' prediction of the event was accurate to within four months. The study began in 1998 and is ongoing.
"This is not something we could start rolling out tomorrow," said William Ledger, a fertility expert at the University of Sheffield, who was not linked to the research. "But if it really does work, it could be immensely useful to young women who are making choices about whether to work or have a family."
Previous studies in Canada, the U.S. and elsewhere have suggested analyzing AMH could help predict when women will go into menopause, but no long-term studies have yet been finished.
"If our model is validated, then women in their 20s could take a blood test and we could provide them with a good estimate of what her age will be at menopause," said Dr. Ramezani Tehrani, an associate professor at Shahid Beheshti University of Medical Sciences in Tehran, who led the study.
Some experts, however, were skeptical a single blood test on young women could be so revealing. "The principle of measuring AMH is reasonable, but I am not sure you could predict (menopause) decades in advance with one test," said Nick Panay, a consultant gynecologist at Hammersmith, Queen Charlotte's and Chelsea Hospitals in London. He thought it might be necessary to test women more often as they got older to monitor if hormone levels dropped off, an indication menopause was imminent.
Doctors said more data should be available about the test's reliability in about five to six years.
"If we're using a test to advise women about when to have children or to have (in-vitro fertilization), then it needs to be a very robust test," said Dr. Nicholas Macklon, a professor of obstetrics and gynecology at the University of Southampton. He said analyzing AMH was a reasonable way to predict menopause, but that it needed to be validated by tracking thousands more women after they became menopausal.
"It will be extremely valuable to be able to tell women how fast their biological clock is ticking," he said. "But people will be making extremely important decisions based on this, so we need to have all the data first."