'Double fertility risk' of women in 'O'blood group

Breakthrough: Research has discovered that women with blood group O are twice as likely to run out of eggs

Women with the most common blood type could be twice as likely to suffer fertility problems, scientists say.

Researchers found that those with blood group O are at much higher risk of running out of healthy eggs, so could have problems conceiving as they get older.

The breakthrough could lead to women basing their decision on whether to pursue a career or start a family on their blood type, experts said.

Almost half the population – 44 per cent – have blood type O. Another 42 per cent have type A and 14 per cent have type AB.

But many women do not know which group they are in and find out only when giving blood or during tests when pregnant or ill.

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 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 – a chemical in the blood which, if high, indicates a woman has a poor ovarian reserve.

FSH levels greater than ten suggest a woman will have more difficulty conceiving. The study, which will be presented at the American Society for Reproductive Medicine in Denver, Colorado, found that those with blood type O were twice as likely to have FSH levels above ten.

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

But they acknowledged that many ‘type O’ women have successfully had children and that there are dozens of other factors affecting fertility such as age, body weight and alcohol consumption.

Experts will now carry out research to test whether those with blood type O have taken longer to conceive or are more likely to need IVF.

Blood type is determined by the make-up of certain proteins on the surface of the blood, known as antigens. Those with blood type O lack the A antigen.

Dr 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’.

‘Patients with blood type O seeking infertility evaluation have a higher likelihood to be diagnosed with elevated FSH and hence manifest diminished ovarian reserve.

‘Women with blood type O are lacking the A or B antigen – from what we understand.’

People with blood type A or AB are more likely to suffer heart disease and strokes, while those with type O are more at risk from arthritis and certain stomach infections such as E-coli.

There is even a blood group diet – advocated by celebrities including Cheryl Cole – based on the theory that different types find it easier to metabolise certain foods.

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