Image caption More than half of all eggs analysed have abnormalities

A new egg screening technique, which doctors hope will boost the success rate of IVF, can predict genetic problems in 90% of cases, research shows.

However, it is not yet clear whether or not it increases pregnancy rates, European fertility experts warned.

Some clinics already offer the £2,000 test to older women who have failed multiple attempts at IVF.

A large trial is due to start next year to further assess the technology.

Up to half of the eggs in younger women and up to 75% in women over 39 are chromosomally abnormal.

Fertility doctors want a reliable way of finding which eggs are genetically sound to try to boost the chances of IVF success.

Delegates at the European Society of Human Reproduction and Embryology (ESHRE) conference in Rome heard that the egg-screening method may be safer and more accurate than other tests which look for genetic problems in cells taken from the developing embryo.

We need a randomised controlled trial to demonstrate this test is going to be of additional benefit on what we already do Tony Rutherford, British Fertility Society

It detects problems by testing a by-product of the egg called the polar body, which contains a carbon copy of the genetic material in the egg, enabling doctors to see if there are too many or too few chromosomes.

The latest analysis of around 200 eggs from 41 couples has proven that it is a reliable method for picking up genetic problems.

Trials needed

But as only eight pregnancies were achieved in the small study, it is not yet possible to say how successful the technique is in boosting birth rates.

Professor Joep Geraedts, who led the ESHRE taskforce on analysing the test, said they were now planning a large trial of several hundred women to see if it has the potential that some claim.

He said that he did have concerns about clinics offering the technique before it had been properly tested.

"I hope it will improve pregnancy rates but I can't say that - that's why we need another trial."

Professor Simon Fishel, managing director of Care Fertility, who pioneered the test and who has now carried out this treatment in more than 150 women, says his data shows it doubles the chance of pregnancy.

"What I'm very pleased about is they have confirmed that what we started is the way to go forward.

"What we haven't yet got from the ESHRE taskforce is any assessment of clinical potential.

"If this technology proves as robust as we think it is, then logic tells us all patients should benefit, not just the older ones."

The chairman of the British Fertility Society, Tony Rutherford, said the results were an important advance, but that women should only be given the test as part of a research study.

"We need a randomised controlled trial to demonstrate this test is going to be of additional benefit on what we already do."