Scientists from Yale University, US, have developed a new technique to improve IVF efficiency from a current success rate of around 34 per cent, to more than 80 per cent in a pilot study. Fertility clinics usually study newly fertilised embryos under a microscope to determine if they are developing in a normal way and to see which seem the most likely to successfully implant. Emre Seli and his team have developed a more advanced method of analysing which embryos are healthy by studying cell metabolism. The team sample a small amount of the fluid embryos grow in before they are transferred into the woman and then perform a type of spectral analysis to detect levels of free radicals, a by-product of normal metabolism. Embryos with normal metabolism have higher levels of free radicals than unhealthy ones.
In a study of 108 embryos tested three days after fertilisation, Seli's team predicted which ones would implant successfully with 80 to 83 per cent accuracy. It is hoped that in addition to improving the overall success rate of IVF, this work could help to reduce multiple pregnancies which is associated with higher risks during pregnancy and childbirth. As success rates can be so low using IVF, multiple embryos may be transferred to the uterus, a practice which is particularly common in the US where there are fewer restrictions than in Europe. The work was presented at the recent annual conference of the American Society for Reproductive Medicine (ASRM) in New Orleans; a large follow up study is now underway.
In related research, a team from the Fertility Centers of New England in Reading, Massachusetts, has begun analysing respiration rates from eggs or newly fertilised embryos to identify the best candidates for fertilisation and implantation. The eggs or embryos are placed into narrow wells so that the air above the nutrient fluid can easily be tested for oxygen levels. A healthily respiring embryo or egg should have depleted oxygen levels above the fluid. In normal development the cells begin to differentiate around five days after fertilisation, with an associated increase in respiration levels. In unhealthy embryos respiration slows or stops. The test has already been used to select viable eggs or embryos in cattle and fertilisation rates increased by 50 per cent. Lead researcher Lynette Scott has confirmed that the technique also works in humans. 'I think this could be a godsend', she commented. The technique could be particularly important for countries such as Italy where selection for implantation is made before fertilisation for ethical reasons.