LONDON – Women with the most common blood type could be twice as likely to suffer fertility problems. Those with blood group ‘O’ are at much higher risk of running out of healthy eggs, so they could have problems conceiving as they age, researchers have found.

Almost half the population – 44 percent – have blood type ‘O’. Another 42 percent have type ‘A’ and 14 percent have type ‘AB’, reports the Daily Mail.

American researchers found that those with blood type ‘O’ were twice as likely to have low ‘ovarian reserve’ – the number of healthy eggs left – than those with other types.

The size of a woman’s ovarian reserve gradually falls throughout her life. A newborn girl has up to two million eggs, but by the time she reaches puberty this has fallen to 400,000 and once she is over 40 she will have just a few hundred left.

Researchers from the Yale University and the Albert Einstein College of Medicine, New York, looked at the blood type of 563 women under 45 who were undergoing fertility treatment.

They compared their levels of Follicle Stimulating Hormone (FSH) – a chemical in the blood which, if high indicates a woman has a poor ovarian reserve, said an Yale release.

FSH levels greater than 10 suggest a woman will have more difficulty conceiving.

Women are deemed infertile with FSH levels higher than 20. The researchers said that in future women could make decisions on when to start a family based on their blood type.

Edward Nejat from the Albert Einstein College of Medicine said: “We found that women with blood type ‘A’ and ‘AB’ – women with the ‘A’ blood group gene – were protected from diminished ovarian reserve.”

Tony Rutherford, chair of the British Fertility Society, said: “This is the first time that I’m aware of researchers having shown a link between blood group and potential for fertility.”

These findings will be presented at the American Society for Reproductive Medicine in Denver, Colorado, US.