Levels of the first two drop as a woman approaches menopause, while FSH levels rise. Taking the three together provides a guide to fertility which tends to plummet after the age of 35.
Women who buy the test by mail order, or through the internet, have a blood sample taken by their GP.
This is sent back to the kit's maker, where analysis gives a guide to the number of healthy eggs in her ovaries - and so her fertility.
The woman is then told how her fertility compares with others her age. For instance, she could be 32 but have the fertility of a 40 year old.
If her fertility is poor, she will be offered counselling. She may also be advised to visit her GP, who may decide she starts trying for a baby straight away.
If her fertility is rated good or average, she will be advised to take the test again two years later, to show how quickly her fertility is declining.
Research published this week shows the Plan Ahead blood test could also benefit women about to undergo fertility treatment.
Used in advance of IVF, it would give women judged to have a low chance of success time to prepare emotionally for the heartache of failing to conceive.
It could also allow those judged to be the least fertile to decide against having IVF, which costs up to £7,000 a time.
Prof Ledger said: "I don't think you can persuade a woman not to have a go with IVF because they are really desperate and it is a life-changing thing to decide you'll never have children.
"But you can soften the blow if you warn them from the start that the hormone results are dreadful and the chance of getting eggs, let alone embryos and babies is less than say, five per cent."
The test could also be used to dissuade the least fertile women from going through the trauma of repeated cycles of IVF.
Prof Ledger said: "Maybe doing this kind of measurement helps to convince women it time to stop."
In a paper published in the journal Human Reproduction, Prof Ledger showed the value of the test in predicting the success of IVF.
The study of 84 women aged 40 and over correlated levels of the hormones measured by Plan Ahead with egg production and conception.
Those with the lowest hormone levels produced the lowest number of eggs and were the less likely to conceive.
The test has been welcomed by fertility charities.
They caution, however, that it is not however foolproof, with problems such as blocked fallopian tubes and low sperm counts outwith its scope.
Taking the test cannot alter the fact that older mothers are at higher risk of problem pregnancies, miscarriages and still births.
They also run a higher risk of having babies with Down's syndrome and other genetic disorders.
Clare Brown, of Infertility Network UK, said: "Although the test results could point to a potential problem and perhaps lead women to seek advice early, a normal result could lull a woman into a false sense of security about her fertility.
"We would stress that women should be careful not to rely solely on these test results as an accurate indicator of future fertility."
Despite the risks associated with getting pregnant later in life, more and more women are ignoring their biological clocks by putting off having children for as long as possible.
Almost half of births in 2003 were to mothers aged 30-plus. Twenty years ago, just 27 per cent of births were to mothers in that age range.
Writing in the British Medical Journal last year, leading doctors warned that women who put off having children until their 30s are "defying Nature" and risking the heartbreak of infertility.
Lead author, Dr Susan Bewley, consultant obstetrician at Guy's and St Thomas' Hospital in London, said: "Women want to 'have it all', but biology is unchanged," she said. "If women want room to manoeuvre, they are unwise to wait until their 30s."
• Plan Ahead can be ordered from Lifestyle Choices on 0114 275 5723 or by logging on to www.Boots.com |
