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.