Blood type 'influences chances of getting pregnant'
Scientists have discovered for the first time that a woman's blood group could influence her chances of getting pregnant.
Those with blood type O may struggle to conceive due to a lower egg count and poorer egg quality, according to a new study.
Meanwhile, women with blood group A seem to be better protected against falling egg counts.
The finding could mean experts look more closely at blood group when charting a woman's fertility.
More than 560 women with an average age of 35 undergoing fertility treatment took part in the latest research, led by experts from Albert Einstein College of Medicine in New York and Yale University.
Blood samples were taken to measure levels of follicle stimulating hormone (FSH), a well known marker of fertility.
FSH levels greater than 10 suggest a woman will have more difficulty conceiving than those whose levels are under 10.
A high FSH level indicates a diminished ovarian reserve, which refers to both egg quality and the number of eggs left available for fertilisation.
Ovarian reserve tends to decline significantly as a woman reaches her middle and late 30s and more quickly in the early 40s.
The study found that women who were blood type O were twice as likely to have an FSH level greater than 10 as those in any other blood group.
The findings held true even when a woman's age was taken into account and the fact the women came from two different clinics.
Those with blood group A were "significantly less likely" to have an FSH level greater than 10 than those who were blood group O. Some 44pc of the Irish population are blood group O and 42pc are type A.
People with blood group A carry the A antigen, which is a protein on the surface of the cell, but this is absent in people with O type.
Dr Edward Nejat, from the department of obstetrics and gynaecology at Albert Einstein College, presented his findings at the American Society for Reproductive Medicine conference in Denver.
He said: "In both groups of women that were seeking fertility treatment, 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 A and AB -- women with the A blood group gene -- were protected from this effect of diminished ovarian reserve."
Dr Nejat said FSH levels were just one marker of fertility and more studies were needed.
"A woman's age remains the most important factor in determining her success of conceiving," he said.
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." However, he said there were other hormones that predicted diminished ovarian reserve that should be assessed.
"This is interesting and it shows a potential link but we really need to look at it with other, more up-to-date tests of ovarian reserve," he said, adding that the issue needed "further exploration".