COPENHAGEN, Denmark — New research indicates that women who become pregnant with donated eggs are more likely to suffer miscarriages and dangerous high blood pressure than those who undergo fertility treatments with their own eggs.

In a study presented Tuesday at the annual meeting of the European Society of Human Reproduction and Embryology, Korean scientists reported that the risk was even higher if the donated egg came from a woman who was not related to the patient.

Previous studies have shown that high blood pressure is more common in pregnancies from donated eggs, but it has been unclear why.

Experts said latest findings indicate the greater risks are due to the fact that donated eggs, like transplanted organs or tissue, are not genetically identical to the recipient and probably awaken the immune system.

The placenta formed after egg donation may have more foreign elements and trigger abnormal responses from the mother, which could result in complications, such as miscarriages or high blood pressure.

Eggs from strangers likely trigger a heavier immune reaction than eggs from a relative, experts said, adding that the findings suggest women who need donated eggs might be better off with eggs from a relative.

In the study, conducted by Dr. SunHwa Cha of Sungkyunkwan University School of Medicine in Seoul, South Korea, 61 pregnancies involving egg donation were compared with a matched group of pregnancies achieved through standard infertility treatment.

Pregnancy induced high blood pressure -- which can become life-threatening to mother and baby -- occurred in 12.5 per cent of the women who got donated eggs and in 3.7 per cent of the women who used their own eggs.

The problem was twice as likely to occur following egg donation from a sister, but more than five times as likely following egg donation from a stranger, the study found.