LONDON, July 16 (Xinhua) -- A new study by UK scientists shows that the blood test for women who repeatedly suffer miscarriages early in pregnancy is ineffective.

The test is generally offered by fertility clinics to measure the level of immune cells called natural killer (NK) cells in the blood and high numbers of NK cells belonging to the mother found close to the outermost layers of the embryo are known linked to miscarriages.

But researchers from Imperial College London found in study that testing for peripheral NK cells may be useless, New Scientist reported on Saturday.

The scientists took blood samples from 405 non-pregnant women who had experienced recurrent early miscarriage and found that the number of peripheral NK cells in these women did not fluctuate with their menstrual cycles, unlike uterine NK cell levels, which are known to increase around the time of ovulation, suggesting that changes in levels of uterine NK cells are not reflected in the blood.

Confirming this by taking uterine biopsies from 23 women at the same time as the blood samples, the scientists found no correlation between peripheral and uterine NK cell numbers.

They also studied 67 women with a history of recurrent miscarriage and found that peripheral NK cell numbers in women who subsequently became pregnant and gave birth to healthy babies were no different to those in women who continued to suffer miscarriages - a condition that affects around 1 in 50 women.

"Measurement of peripheral blood NK cells is a poor predictor of pregnancy outcomes," leading researcher Raj Rai was quoted as saying.

According to the New Scientist report, other researchers said emerging evidence suggests that it may be certain properties of NKcells, rather than their number, that determine the likelihood of miscarriage. Enditem