By JEREMY LAURANCE
A genetic test to tell career women how long they can safely wait until starting a family could be available in five years.
As more women have moved into the workplace the average age at which they give birth has risen, with many waiting until their
early 40s.
The number of women aged 35 and over in Britain giving birth rose from 31,000 in 1977 to 100,000 last year, according to the Office for National Statistics.
But fertility declines with age and women who leave childbearing late may find themselves unable to conceive. A test enabling women to tell when their fertility was likely to decline would help millions to make career decisions.
Dutch researchers studied the age of menopause, which is known to be linked with the age at which fertility declines, in 100 pairs of sisters to see if it was inherited. The normal age of menopause is between 47 and 52.
Previous research by the team showed fertility declining about 20 years before the menopause.
The researchers collected information from 243 sisters in 118 families. They also studied 22 non-identical and 37 identical twins.
The results, published in Human Reproduction, show the age of menopause is 85 per cent genetically determined.
Dr Jan-Peter de Bruin, research leader of the department of obstetrics and gynaecology at the University Medical Centre in Utrecht, said: "The age at which women become pregnant with their first child is one of the most remarkable demographic changes in the last 30 to 40 years.
"More and more women will face childlessness if this trend keeps going."
The researchers are collecting genetic material from the sisters to identify genes for controlling the menopause which could pave the way to a test.
Dr de Bruin said: "We expect to have results in about five years. If we do succeed in isolating the responsible genes it is possible that women in the future will be able to have a DNA test that will predict their age of menopause."
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