A new pre-implantation genetic screening technique may improve the chances of conception for patients undergoing IVF, a recent study reveals. At present IVF success rates are at around 30 per cent but by screening embryos prior to implantation this can be improved by avoiding common problems which can result in miscarriage or the embryo failing to implant.
The technique, called comparative genomic hybridisation (CGH), differs from other screening tests in that it tests all 24 chromosomes in the developing embryo for abnormalities. Pre-implantation screening allows doctors to select the 'best' embryos to implant back into the womb. Speaking in The Times newspaper, Tony Rutherford, Chairman of the British Fertility Society, explained that 'in between half and three quarters of cases, the cause is an embryo with abnormal chromosomes, flaws that cannot be spotted under the microscope.' Older women tend to carry a higher risk of genetic defects in their eggs but screening the embryos can mean genetic disorders like Down syndrome can be avoided and the risk of miscarriage lowered.
The procedure was developed by Dr Dagan Wells, a Senior Fellow in Reproductive Genetics at the University of Oxford. The study looked at 115 women aged around 39 and with a history of unsuccessful IVF attempts. The results, to be presented at the American Society for Reproductive Medicine's annual conference in Atlanta, US, this week, showed that around two thirds of the women whose embryos were tested by CGH became pregnant compared with under one third of women who did not undergo CGH. 'We were taken aback by the impact it had on the success rates,' said Dr Wells, adding: 'I think it's at the point now that we can say with great confidence that we are seeing a positive effect of this.'
Dr Allan Pacey of the British Fertility Society welcomed the news saying that 'embryology is really crying out for something like this... We really haven't moved on from the science of just looking down the microscope and seeing if an embryo looks good on the basis of some rather loose criteria.' Susan Seenan, from the Infertility Network UK, also welcomed the findings but highlighted that in the UK many NHS trusts are still failing to meet guidelines issued by the National Institute of Health and Clinical Excellence (NICE) which recommend that infertile couples should be offered three free cycles of IVF. 'Improvements in success rates are always important but even more so where patients are receiving only one, or in some cases, no NHS cycles, and we look forward to seeing if further research confirms these results,' she said.
Dr Wells told reporters that more than twenty babies have been born in the United States following CGH. The test costs £2,000 but is at present only available in a small number of private fertility clinics in the UK.
