Time no longer running out for ‘biological clock’

Wednesday 16 June 2004

A computer scientist at the University of Andrews has developed a ground-breaking formula for working out when a woman’s ‘biological clock’ is likely to stop ticking.

The mathematical method developed by Dr Tom Kelsey, in collaboration with Edinburgh-based oncologist Dr Hamish Wallace, gives doctors a method for predicting how long a woman has before she reaches the menopause.

By providing an assessment of the number of cells (eggs) within the ovaries, the researchers can predict a woman’s remaining ‘reproductive life- span’. The method will revolutionise the treatment of women seeking assisted conception, those who have had treatment for childhood cancer and those who wish to delay a family for personal or professional reasons.

In theory, women from the ages of 25-50 will be able to find out how many ‘fertile’ years they have left, by having a simple ultrasound. The method, much in the same way that doctors can look at an unborn baby to check its health, will allow doctors to check the health (and importantly the size) of the ovaries. Using further mathematical and computer analysis, it is possible to work out when the ovaries are likely to stop producing eggs.

Dr Wallace, of Edinburgh’s Royal Hospital for Sick Children, said: “The age of menopause varies from woman to woman and there is currently no reliable test of ovarian reserve for an individual woman that will predict accurately her remaining reproductive life- span. What we have done is to come up with a method that may allow us to predict for a woman, aged 25-50 years, what ovarian reserves she has and at what age she is likely to experience the menopause.

“In essence, 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,” he continued.

Drs Kelsey and Wallace came across the discovery as a by-product of their main study area of working out likely menopause age in young females who have had cancer. Because exposure to radiation in any part of the body can kill ovarian cells and therefore impair fertility, the method is used to inform the young women or their parents of the likely age of early menopause, so that they can make advance family planning decisions if necessary.

After several years work in this field, the researchers realised that the predicted reproductive lifespan could be calculated in exactly the same way for healthy women.

Dr Kelsey is the scientist behind the mathematical modelling, while Dr Wallace is the oncologist with the medical expertise, and together they have developed the ‘Wallace-Kelsey method’. The method can be used from a very young age as the number of ovarian cells is determined at birth. On average, females begin with a few hundred thousand cells and usually, by the average menopause age of 50, the number decreases to just 1,000, which is not enough to generate eggs.

The key to the method lies in the mathematical modelling of the ovaries, so that the size and number of cells can be calculated. Using statistical tables already developed, the Wallace-Kelsey method can be used to work out roughly how many fertile years are left.

Dr Kelsey, of the University’s School of Computer Science said:

“Ultrasound is an ideal method, because it is safe, non- destructive and relatively cheap. The technology already 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.”

The method was developed using data supplied by an ultrasound study conducted on healthy Western women aged between 25 and 50. The method will work on most women, but, for example, cannot be used on those taking oral contraception. There are two inherent assumptions in the calculations – both shown in other research to be reliable – that variation in age at menopause is due to wide variation in the number of eggs present at birth, and that ovarian size between the ages of 25 and 50 is directly related to the remaining number of eggs.

Drs Kelsey and Wallace are currently talking to GPs, fertility clinics and the University of St Andrews’ Bute Medical School to explore the way forward for their pioneering method.

The findings are reported in Europe’s leading reproductive medicine journal ‘Human Reproduction’, published today.



DR KELSEY IS AVAILABLE FOR INTERVIEW TOMORROW (WEDNESDAY 16TH JUNE) ON 01334 463247 / 07900 283 177 OR EMAIL [email protected] andrews.ac.uk


THE FULL PAPER IS AVAILABLE FROM THE OUP: Contact (media inquiries only): Margaret Willson: Tel: 01536 772181, Mobile: 07973 853347, Email: [email protected]

Issued by Beattie Media On behalf of the University of St Andrews Contact Gayle Cook on 01334 467227, mobile 07900 050 103, or email [email protected] Ref: Biological clock pr 150604.doc View the latest University news at http://www.st-andrews.ac.uk

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