New test boosts pregnancy success rate for women undergoing IVF
Women undergoing IVF could have an 80pc chance of success thanks to a new test developed by British scientists.
The test looks at how mitochondria - which are crucial for the development of healthy babies - behave inside each embryo.
Experts have discovered that some embryos have far too much mitochondrial DNA (mtDNA) and will never develop into a baby.
Mitochondria have a key role during embryo development. They are the main energy providers and have other critical functions.
The fertility world is so impressed by the new findings from the University of Oxford that the work has been shortlisted for two major prizes.
Professor Dagan Wells, from the university, said the test could be very beneficial for couples who often face a "difficult journey" through fertility treatment.
He said the majority of embryos created through IVF "have no chance at all" of resulting in a successful pregnancy.
Only around a third of IVF transfers in the UK are successful.
The figure is rising by about 1% a year but it is "painfully slow", Professor Wells said.
A woman who produces eight embryos, for example, may have only one that will result in pregnancy.
"You are potentially putting your patient through eight embryo transfers before you get to the one embryo that is viable," he said.
"For the patient repeatedly having negative pregnancy tests, that's brutal.
"Any test of the embryo that will result in a baby is therefore highly desirable."
The new test, which could be available in the UK from next year, could hugely boost IVF success rates.
A clinical trial carried out in New York has resulted in a pregnancy success rate of around 80%.
The test involves embryos that have been grown in the laboratory until they are five days old (the blastocyst stage).
At this time, embryos are made up of around 100 cells, of which five are removed for testing.
Scientists already know that more than half of all embryos are chromosomally abnormal and will not result in a baby.
Even of those embryos that are chromosomally normal, a third will still not implant.
The new tests involves usual chromosomal screening then looking closely at why the remaining embryos are still not resulting in a baby.
Prof Wells said: "What we have found is that a significant number of embryos have unusually high levels of mitochondrial DNA and have too much of it.
"Having mtDNA above a certain threshold seems incompatible with implantation of an embryo."
Prof Wells said it is still unclear why the embryos produce too much mtDNA. New work will try to find out why this is.
He said he hoped that at some point in the future, chromosomal testing plus the new mtDNA test would be available on the NHS rather than just through private IVF clinics.
"It is very high benefit," he said.
The new work has been shortlisted for a prize from the Society for Assisted Reproductive Technology in the US.
It has also been shortlisted for the main conference prize at the American Society for Reproductive Medicine (ASRM) conference being held in Baltimore.
Stuart Lavery, consultant gynaecologist and honorary senior lecturer in reproductive medicine at Imperial College London, said: "This important research sheds more light on our understanding of early human embryo development.
"IVF remains a very inefficient process, with many embryos generated not leading to a pregnancy.
"This new finding of mitochondrial assessment in human embryos could offer an additional opportunity to screen embryos prior to implantation, helping patients get pregnant quicker."
In 2013, 49,636 women in the UK underwent IVF.