Test for ticking biological clock

By Dr. Ananya Mandal, MDAug 9 2011

Researchers from St Andrews University, Scotland have been able to chart the levels of a vital fertility hormone in women of different ages thus essentially detect their biological clocks.

The team believes this could help family planning by predicting when a woman is likely to start the menopause and may ultimately show how long she can delay having children. It could also save couples expensive – but ultimately futile – in vitro fertilisation treatments by predicting their chances of successful conception.

The team in collaboration with scientists from Glasgow and Edinburgh universities compared hormone levels in 3,200 healthy women to show accurately how the range changed with age. Tom Kelsey, a lecturer in the university’s school of computer science, who helped the research, said it was already known that high levels of the fertility hormone were good for conception “but we could not back that up statistically”. “This study now provides us with the level you would expect to find in a normal, healthy woman,” he said.

Researchers explain that women are born with a finite supply of eggs – on average between one and two million – which are shed as part of the monthly cycle until menopause. A woman’s ability to conceive declines substantially after her mid-30s. This speed however differs between individuals.

The latest study examined levels of anti-Mullerian hormones (AMH), which reflect ovarian activity and give an estimate of remaining egg supply. The study found that AMH levels peaked at the age of 24 but had almost halved by the time women were in their mid-30s and were almost non-existent by their late 40s. 

Richard Anderson, professor of reproductive medicine at Edinburgh University, said, “Predicting how long you might remain fertile can be very important, and it seems that AMH can help in this.”

Professor Scott Nelson, from the University of Glasgow, said a major use of the new findings could be in helping young cancer patients wondering how their treatment may have affected their chances of having a baby. “We can now see 18-year-old girls, know what their AMH is and put that into context,” he said. He added that if women of any reproductive age were struggling to get pregnant, the refined information could be used to indicate whether their AMH levels are normal for their age or below average. This could suggest how soon they might have to start thinking about fertility treatment such as IVF.

However, Prof Nelson said he would not recommend women in their 30s delaying having a baby because the AMH test appeared to suggest they had a certain number of fertile years left. “It might be useful if you are much younger and in your 20s, but not in your mid-30s. For example, Down's syndrome risk is one in 250 at 35, but by the time you are 40 it is one in 100…If you wait those few years that risk is going to increase,” he said.

A recent paper published in The Obstetrician & Gynecologist journal said women could be at “substantive risk” of complications such as heart disease and even stillbirth for their babies.