By the age of 30 there is only 12 per cent of eggs left

By Simret Samra

Scientists have discovered the reason why women find it difficult to conceive later in life – they have used up 90 per cent of their “ovarian reserve” by the age of 30

The new research by the University of St Andrews and Edinburgh University is the first to look at the actual decline of the “ovarian reserve” – the potential number of eggs women are born with from conception to menopause.

It shows that on average women are born with 300,000 potential egg cells but this pool declines at a much faster rate than first thought.

By the age of 30 there is only 12 per cent left on average and by the age of 40 just three per cent.

This finding sheds new light on the saying “the clock is ticking” for women who want to conceive.

Dr Hamish Wallace, the co-author said: “Our research shows that they are generally over-estimating their fertility prospect.”

“Our model shows that for 95 per cent of women, the age of 30 years, only 12% of their maximum ovarian reserve is present, and by the age of 40 years, only three per cent remains.”

Dr Wallace, at Edinburgh’s Royal Hospital for Sick Children, added that the research could help predict which women have early menopause and when to freeze eggs from ovarian cancer victims.