美国一项新研究发现，随着年龄的增加，O型血的女性受孕会更困难，这是首个有关血型会影响女性受孕几率的研究。纽约市爱因斯坦医学院的研究人员对560名平均年龄在35岁以下、正在接受不孕症治疗的女性进行了调查，结果发现，O型血的女性在排卵数量和卵子质量方面都要弱于其他女性。相比之下，A型血的女性排卵数量更多，卵子质量也要更好。该研究还发现，O型血女性的卵泡刺激素(FSH)水平比A型血女性更高。生育专家指出，FSH水平是卵子数量的重要标志。女性体内产生FSH主要是刺激卵巢中的卵泡。当三四十岁女性的卵巢中卵子耗尽时，其身体就会自动产生更多的FSH，以刺激排卵。因此，FSH水平过高就意味着卵子数量更少。该研究显示，O型血妇女FSH水平超过10的可能性是其它血型妇女的两倍。A型血者带有A抗原，而O型血者则缺少这种具有保护作用的抗原。

A woman's blood group could influence her chances of getting pregnant.

Women with blood type O could have more trouble conceiving as they age, an American survey claims.

The study is the first to suggest that a woman's blood group could influence her chances of getting pregnant.

Researchers who tested a group of women seeking fertility treatment found those with the blood type O appeared to have a lower egg count and poorer egg quality than others.

By contrast those with blood type A seemed to have more and better quality eggs.

The findings could lead to women with type O blood being advised to try for a baby earlier, but experts said more research was needed before such a step was taken.

The blood groups O and A are the two most common in the British population: some 44 per cent are type O and 42 per cent are type A.

The lead author, Dr Edward Nejat, of the department of obstetrics and gynaecology at the Albert Einstein College of Medicine in New York, said his findings were based on women having fertility treatment at the Yale University IVF programme and the Montefiore Institute in New York.

He is presenting his findings tomorrow at the annual American Society for Reproductive Medicine (ASRM) conference in Denver.

The study of 560 women, whose average age was just under 35, found that those with blood type O were more likely to have higher levels of "follicle stimulating hormone" (FSH) than those with type A.

Fertility experts regard a high FSH level as a key indicator of having a low egg count. FSH is produced by the body to stimulate the follicles in the ovaries that produce eggs.

As a woman's ovaries run out of eggs in her 30s and 40s, production therefore has to be stepped up to encourage more eggs. The presence of high levels of FSH indicates lower numbers of eggs.

The study found that women with blood type O were twice as likely to have an FSH level above 10 – regarded as the threshold between normal and raised levels – as those in any other blood group.

People with blood group A carry the A antigen, a protein on the cell surface, that is absent in people with O type.

Dr Nejat said: "Those with blood type O were twice as likely to have an FSH level over 10 than those with blood types other than O. We found that women with the A blood group gene were protected from this effect."

Susan Seenan, of Infertility Network UK, welcomed the study. "Anything that might help couples avoid having fertility treatment has got to be good news," she said.

Tony Rutherford, the chairman of the British Fertility Society, said the research was "interesting".

But he said a study needed to be carried out among the general population, not just those who had gone for help with fertility problems.