Blood type O link to fertility problems

25^th October 2010 - Researchers say having type O blood can affect a woman’s chances of getting pregnant.

Scientists from Yale, Montifore and Albert Einstein College of Medicine in the US have produced a study which finds patients with type O blood were at double the risk of diminished ovarian (egg) reserve than women of other blood types.

They’re presenting their results to the American Society for Reproductive Medicine (ASRM) annual conference in Denver.

However one UK expert on fertility says more research needs to be done after these “surprising and stark” findings.

The study

Researchers measured women, under age 45, for levels of the reproductive hormone FSH. Women with an FSH level greater than 10 are considered to have diminished ovarian reserve. 

They made adjustments for other fertility factors: age and BMI (body mass index), then compared women’s blood types and FSH levels. 

Women with type A or AB blood types were significantly less likely to have an FSH greater than 10 than were women with O or B blood types.

“This is a novel look at a poorly understand part of reproductive ageing. Through studies like these we will be better able to understand the complexities of the human reproductive system,” says Dr William Gibbons, President of the ASRM.

In the UK, 44% of the population is type O, 42% type A, 10% type B and 4% AB.

More research needed

Professor Richard Fleming, is a director of the Glasgow Centre for Reproductive Medicine. “The results do seem quite surprising and stark in the distribution that you see between the blood groups,” he tells us.

However, he cautions that the FSH method used to measure fertility in the US study isn’t the most accurate available: “The method used to diagnose the state of ovarian reserve in this study is really not the best way of testing.

“It is fairly good at assessing extremes of egg reserve, but it can’t differentiate between normal and high and perhaps not even low normal.”

He says a better test is to get a woman’s anti-mullerian hormones measured. The newer test is more expensive than FSH. It is available through fertility professionals, but not always on the NHS. “It is a more precise marker of ovarian reserve,” he tells us.

Should women with type O blood wanting to have a baby worry? “It is an interesting, and to me, quite surprising finding, that needs to be substantiated. Therefore, the implication for someone with type O is number one: don’t worry.”

“Number two,” if women have fertility concerns, Fleming says, “get their AMH measured not their FSH.”