Scientists have developed a method that aims to predict how fast a woman’s biological clock is ticking and when she is likely to go through menopause.

They say the test will also help women who are considering whether to delay having children, for professional or personal reasons.

By measuring the volume of ovaries with ultrasound, researchers in Scotland said on Thursday they can predict the reproductive age of a woman aged 25 to 51, or how many eggs she may have left, which could dramatically change fertility treatments.

“What we have done is to come up with a method that may allow us to predict for a woman what ovarian reserves she has and at what age she is likely to experience the menopause,” said Dr Hamish Wallace, a paediatric oncologist and lecturer at the University of Edinburgh.

Women are born with an estimated 800,000 eggs but the number dwindles with age. At about 37, when there are about 25,000 eggs left, the decline speeds up and the ovaries shrink until most of the eggs are depleted and menopause occurs.

The age of menopause is generally around 50, plus or minus seven or eight years. Knowing a woman’s reproductive lifespan will enable doctors to predict how long she will be fertile and whether she will have an early menopause.

Dr Thomas Kelsey, a computer expert at the University of St Andrews, said the main benefit of the research would be to improve fertility treatment and planning and to provide doctors with information about the likely success of such treatments.

“The ultrasound measurement is taken to work out the volume of the ovaries. If the ovaries are larger than average for her age, then she is likely to have a later menopause and if they are smaller she is likely to have an earlier one. Essentially we try to quantify by how much, by how many years,” he told Reuters.

Wallace and Kelsey, who reported their research in the journal Human Reproduction, showed a strong relationship between ovarian volume and the number of egg cells.

“It is going to be useful for couples who have fertility problems because it is an easy way for the fertility clinics to work out essentially whether it is worth doing IVF (in-vitro fertilisation) or whatever treatment,” Kelsey added.

If a woman has many more fertile years it may be better to try to conceive naturally or to space out fertility treatments or, if the egg supply is low, not to waste time.

But the method will not work for women taking oral contraception because it decreases the size of the ovaries or for women suffering from polycystic ovarian syndrome, a disorder that causes infertility.

The researchers are conducting clinical studies on women who have been treated for cancer, which can impair fertility, to provide information on their fertility.

They are also planning long-term studies to follow young women until they reach the menopause.

“It opens the door to the possibility of screening women for early ovarian ageing. These women may be at increased risk to their general health from the effects of having an early menopause,” Wallace added in a statement.