New test could boost IVF success to 70pc instead of current 30pc
Published 18/10/2011 | 08:05
SCIENTISTS are developing a test that could dramatically boost IVF success rates from a single cycle of treatment.
The technique, from experts at Oxford University, checks for chromosomal abnormalities in the developing embryo but also looks at two new markers that could potentially cause pregnancies to fail.
Over time, researchers hope they can increase success rates towards the 100pc mark from just one cycle of IVF.
The scientific community is so excited by the novel technique that the study has won a prize from the US Society for Assisted Reproductive Technologies.
At present, only around 30pc of IVF cycles worldwide result in a pregnancy, with many failing due to chromosomal abnormalities.
Dr Dagan Wells's team at Oxford have already pioneered a technique for checking embryos for these abnormalities.
Embryos are grown for five days in the lab and analysed to check the chromosome number.
Only those embryos that are healthy are considered suitable for IVF transfer - increasing the chance of pregnancy to 70pc per cycle.
"The vast majority of embryos transferred worldwide have no genetic screening and 85pc of these fail to establish a pregnancy," Dr Wells said.
"If you transfer to the uterus embryos that are confirmed to be chromosomally normal and develop well, reaching the blastocyst stage, the chance of producing a child is very high, about 70pc.
"But that still leaves 30pc that don't make it. Why? We need a better understanding of the biology, allowing us to bridge that gap and approach 100pc success."
The new technique combines the checking of chromosomes with the appearance of telomeres, which cap chromosomes and are linked to healthy cells.
Another marker examined by the test is the number of mitochondria - the power houses of a cell.
"Chromosomes are a big part of the story but they are not the be all and end all," Dr Wells said.
"There are many aspects of biology that make up a viable pregnancy.
"Two other good candidates that may affect embryo competency are telomeres and mitochondria.
"With the new tool we've developed we can count the chromosomes but we can also look at telomeres, which protect the ends of chromosomes.
"This might be important because longer telomeres are associated with the viability of the cell."
Dr Wells said not all embryos have long telomeres - and those that do not may be more likely to fail.
"It is also possible that the number of mitochondria in the cells of an embryo might also be indicative of their chances of producing a pregnancy," he said.
"Embryos that don't do so well tend to have an abnormally high number of mitochondria."
The test will be particularly useful for older women, who have a higher chance of producing eggs with chromosomal defects, which can cause conditions such as Down's syndrome.
But it could also benefit younger women - maximising their chances of falling pregnant in each IVF cycle.
The next stage of research - which will take around a year - will look in detail at the potentially negative effect of telomeres and mitochondria.
Dr Wells said experts needed to find the "shortfall" in why chromosomally-healthy embryos do not always produce a baby.
"We hope to fill in the gap and get closer to getting a successful pregnancy from every IVF cycle," he said.
"Sometimes, we don't get a pregnancy even though the embryo looks healthy and has the correct number of chromosomes.
"The embryo gets transferred and yet it still doesn't make a baby.
"In the future, we will be able to compare embryos that make a baby and those that don't, and we will be able to determine whether differences in their telomeres are responsible for unsuccessful IVF treatments that are currently unexplained."
Once developed, the test is likely to cost around £2,000 (€2,297) on top of the cost of IVF. It can be used on both eggs and embryos, but ideally on embryos to check a full set of genetic information from both parents.
"However, for some people, testing on eggs is more ethically acceptable because testing may be completed before fertilisation and the creation of an embryo," Dr Wells said.
"Additionally, some patients don't produce embryos that develop well outside the body (in vitro), making it difficult to apply these tests. For them testing eggs may be a good option."
Tony Rutherford, chairman of the British Fertility Society, said: "This exciting novel technique is taking the molecular assessment of the embryo to a new level, and clearly is an important tool for research into embryo health.
"Selecting the right embryo for replacement in a cost-effective, reproducible manner potentially has enormous benefits for patients, clinics and the health service overall.
"Of course, as with any new technology, appropriate clinical studies are required to ensure that the benefits are realised.
"The difficulty we face is making sure adequate funding is made available to allow this new technique to be assessed fully before it enters clinical practice."