Women get timer to biological clock
Using an ultrasound procedure, the test will allow career women to calculate how long they can put motherhood on hold. It will also help others finding it difficult to conceive.
Women could be screened to identify those at risk from an early menopause, which can have adverse effects such as osteoporosis and an increased risk of heart disease.
The test uses ultrasound to measure the size of a woman's ovaries and sophisticated mathematical modelling. Together they provide an accurate estimate of when women are likely to experience the menopause.
Researcher Hamish Wallace, from the Royal Hospital for Sick Children in Edinburgh, said: "It means we now have the potential to be able to tell a woman how fast her biological clock is ticking and how much time she has before it will run down."
Evelyn Mahon, a senior lecturer in sociology at Trinity College Dublin, said the test could help reassure women who have delayed getting pregnant that they are still producing eggs.
Each ovary contains a fixed pool of immature eggs, which form in the womb. They peak at several million in the five-month-old foetus and then start to decline.
By about the age of 37, there are only about 25,000 eggs left, at which point the decline accelerates.
Just before a woman enters the menopause, the number is down to about 1,000 too few to generate a mature egg capable of being fertilised.
The age at which a woman hits the menopause varies. Normally it is at about 50, but it may be sooner or later. Until now, there was no accurate way of predicting when "the change" would occur.
Dr Wallace, working with computer expert Thomas Kelsey from the University of St Andrews in Scotland, developed their technique while researching the likely menopause age of women who had cancer.
Radiotherapy can kill ovarian cells and impair fertility, bringing about an early menopause.
The key to the test is the relationship between the size of the ovaries and the number of follicles the cavities in which immature eggs form they contain.
Ultrasound is used to measure the volume of the ovaries and the information is then used to work out roughly how many fertile years a woman has left.
"Ultrasound is an ideal method, because it is safe, non-destructive and relatively cheap," said Dr Kelsey. "The technology exists and is readily available all over the Western world. It is possible that this service can be made available at GP surgeries or at fertility clinics, and would be a likely first step in the family planning scenario."
