UK researchers are planning a trial of a new test for identifying which IVF embryos are most likely to result in a healthy pregnancy. The technique has already been used to achieve seven successful pregnancies in women who had previously been unable to become pregnant with or without IVF.
The trial, due to commence this autumn, will involve 90 women under the care of Dr Kamal Ahuja, scientific and managing director of the London Women's Clinic. Preliminary trials of the test, carried out in the US last year, were extremely promising, however, the test remains controversial in the absence of robust evidence to indicate its benefit to couples undergoing IVF.
Dr Elpida Fragouli, from the University of Oxford and Reprogenetics, UK, said that her team had so far trialled the test on 35 women with a history of failed IVF attempts and an average age of 42. Of these women 20 per cent achieved a successful pregnancy - more than double that expected for women in this age group and with this medical history.
Speaking at the annual meeting of the European Society for Human Reproduction and Embryology (ESHRE) in Amsterdam today, she said of the initial results: 'This represents a doubling of the usual pregnancy rate for women who fall into this category, which is otherwise, at best, under 10 per cent and, at worst, zero. To date, we have two live births from this group, and all the other women who became pregnant have maintained their pregnancies.'
The new method, known as Comparative Genomic Hybridisation (CGH), uses a laser to cut a hole at the edge of the egg to remove an extra copy of all the egg's chromosomes from a structure known as the 'polar body'. This can then be examined for chromosomal abnormalities without disturbing the main genetic material of the egg itself.
Currently, only one in three IVF treatments will result in a successful pregnancy. Often this is because the egg has an abnormal number of chromosomes, a condition known as 'aneuploidy'. In younger women, 50 per cent of their eggs will have some sort of chromosomal defect. This rises to 75 per cent in women over 40 years old.
CGH has several advantages over conventional screening methods: it allows the full complement of 23 chromosomes to be analysed, it doesn't risk disrupting the developing embryo by removing cells, it can be carried out on unfertilised eggs allowing it to be used in countries where embryo screening is illegal and it can be performed on embryos at the 100-150 cell stage allowing more cells to be tested.