Ultrasound test predicts 'reproductive age'.
It'sthe question every wannabe mother asks: how many years has she got before her biological clock stops ticking? Scientists can now provide the answer, by determining how many eggs are inside a woman's ovaries, and thus how many reproductive years she has left.
"We will certainly see this being widely used, especially for people attending clinics for fertility treatment," says Thomas Kelsey, a computer scientist at the University of St Andrews, Scotland, and an author of the study. If a woman is approaching menopause, she may need fertility treatment sooner than she thought.
The technique measures the size of a woman's ovaries by ultrasound, which produces images of internal body organs using sound-waves. Kelsey, working with reproduction scientist Hamish Wallace from the University of Edinburgh, has analysed data on preserved ovary specimens and shown that an ovary's volume is directly correlated with how many eggs it contains. Their results are published in Human Reproduction1.
The number of a woman's eggs peaks at several million in the female fetus. As a woman ages, the number of eggs declines and the ovaries shrink. At menopause, there are only about 1,000 left.
Kelsey and Wallace analysed data on around 14,000 preserved ovaries to show the relationship between the age of a woman and the volume of her ovaries. They also looked at the relationship between a woman's age and the number of eggs she had left, using data on around 100 ovaries.
They found that the two relationships look very similar, and concluded that ovary size can be used to predict how many eggs a woman has left, and when her menopause should arrive.
Roger Gosden, fertility scientist at the Jones Institute for Reproductive Medicine in Norfolk, Virginia, welcomes the finding but is sceptical about how accurately ovarian volume is related to egg number. "I would be surprised if we got great precision," he says.
But he acknowledges that a new test is required. "We desperately need this," he says. Currently, blood hormone tests are used to indicate egg number, but these do not generally show a decline until just a few years before menopause. "More warning would be great," he says.
Leaving it late
The warning would help women to pursue assisted reproduction techniques, such as in vitro fertilization (IVF), before her egg count falls too low. "This information is good for determining whether a woman needs assisted reproduction," says Henri Leridon, a reproduction scientist at the French National Institute for Health and Medical Research (INSERM) in Paris.
In a different study, also published in Human Reproduction, Leridon produced computer models that compared age-related decline in female fertility and the benefits that assisted reproduction can provide. Women in the developing world are increasingly postponing childbirth. "We wanted to see what can be compensated for by those technologies," says Leridon.
His worrying conclusion was that artificial techniques do not increase an older woman's chance of conceiving to what it would have been earlier in her life2.
Gosden believes that improving assisted reproduction techniques could solve the problem. For example, IVF involves making embryos in a test tube and implanting them into the womb. But it is difficult to detect the healthiest embryos. "If we could identify these," says Gosden, "IVF would be more reliable than even natural, healthy reproduction."
Wallace, H. W. & Kelsey, T. W. . Human Reproduction, 19, 1613 - 1618, (2004).
Leridon, H. . Human Reproduction, 19, 1549 - 1554, (2004).