Infertile couples could double their chances of starting a family by IVF, with an embryo quality test developed by British and American scientists.

The first trial of the procedure, which identifies embryos with the best chances of developing into healthy babies, delivered remarkable results that suggest it could transform IVF success rates, while helping to prevent damaging multiple pregnancies.

Of 23 women to have their embryos genetically screened with the technology, two have given birth while another 16 are currently pregnant and have passed the point at which miscarriages typically occur. Another two became pregnant but miscarried.

The 78 per cent success rate is particularly outstanding because all the patients had a poor prognosis, with an average age of 37½ and a history of failed attempts at IVF or miscarriage.

Dagan Wells, of the University of Oxford, who leads the research team, has applied for permission from the Human Fertilisation and Embryology Authority (HFEA) to offer the test at the Oxford Fertility Unit, and a British trial is expected to begin next year. The test will eventually cost about £2,000.

It could raise success rates when only a single embryo is used. The HFEA has launched a strategy to promote single embryo transfer, to guard against twin and triplet pregnancies – the biggest health risk of IVF.

Dr Wells said: “The pregnancy rates we’ve got so far are absolutely phenomenal.” The probability that one embryo leads to a pregnancy is doubled, he said. “That means that you’ve got a much better chance of a pregnancy if you do a single embryo transfer.”

The new procedure to detect chromosomal defects called aneuploidies was developed by Dr Wells with colleagues from the Colorado Centre for Reproductive Medicine near Denver.

More than half of all embryos are aneuploid, which means they have too many chromosomes or too few. Most of these fail to implant in the womb or miscarry, while the few that survive have chromosomal disorders such as Down’s syndrome.

While a preimplantation genetic test for aneuploidy is already available, it is controversial as there is little evidence that it helps women to conceive. Some studies have even suggested it is harmful, and the British Fertility Society recommends that it should be offered only in clinical trials.

The new approach improves on this by testing IVF embryos when they reach the blastocyst stage of 100 to 150 cells. This allows extra cells to be removed for genetic analysis, giving increased accuracy.

It also employs a more advanced profiling system called comparative genomic hybridisation, which can screen all 23 pairs of chromosomes, against only ten with existing techniques.

CGH can also be used to analyse the genetic quality of eggs before fertilisation, by examining DNA in a discarded structure called the polar body. This is already being offered in the UK by the CARE Fertility Group.

In the trial, which will be presented today at the American Society for Reproductive Medicine conference in San Francisco, patients had IVF at the Colorado centre, and cells were then removed and DNA sent to Oxford for analysis. Once the normal embryos had been identified, these were then implanted. The 78 per cent success rate recorded so far is significantly better than the 60 per cent that the clinic usually achieves for this patient group. For each individual embryo, the implantation rate is 62 per cent, against a normal rate of 28 per cent.

Mandy Katz-Jaffe, of the Colorado centre, said: “This is still a trial, and we don’t offer it yet as a clinical procedure. But this is very promising.” Allan Pacey, of the British Fertility Society, said the results were interesting, but that it would need to see larger studies with a control group before the society changed its policy on preimplantation screening.

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