By Caroline Parkinson
Health reporter, BBC News, Barcelona
Selecting a healthy embryo is difficult
A new test checks the chemical "fingerprint" of the fluid which surrounds IVF embryos to identify those most likely to implant successfully.
The US developers told a European fertility conference it may improve IVF pregnancy rates by up to 15%.
Selecting the embryo most likely to result in a successful pregnancy is the "Holy Grail" of fertility research.
But clinics currently have to select which to use by assessing embryos under a microscope.
Choosing the right embryo from the eight to 10 candidates usually available is key because if there is any damage, or it has not developed properly, the chances of a successful pregnancy are reduced.
It is also increasingly important as IVF doctors move towards implanting just one embryo per treatment cycle to reduce the chance of a multiple birth.
Pregnancy chance boost
The ViaTestE device, developed by scientists from Yale, can score the metabolic activity of a sample of the fluid from around the embryo using spectrophotometry, which uses infrared light to measure the make-up of a substance.
For example, it is used to tell if milk is full-fat or semi-skimmed.
In this instance, the technology checks the activity of metabolites - the substances produced by the embryo.
The team tested around 500 samples of embryo fluid, without knowing which had implanted successfully.
The embryos had also been assessed in the clinics using the traditional method.
That gave around a 40% rate of accurately identifying the embryos which developed into viable foetuses.
But "fingerprinting" using the new test increased that rate to between 60% and 70%.
From these and other results, the scientists believe using the test could improve pregnancy rates by between 10-15%.
That would increase the success rate for women under 35 in the UK receiving IVF from 30% to 45%.
Trials of the test will begin in the Netherlands and Sweden later this year.
But Denny Sakkas, associate professor of obstetrics and gynaecology at Yale University, who is involved in the work, said clinics, including those in the UK, would be able to use the test, marketed by Molecular Biometrics, early next year.
He added: "Everyone's aim is to get patients pregnant, so the greatest impact of using this device would be in improving pregnancy rates by the 10-15% which it appears to have the potential to do.
"And with the move to single embryo transfer, selecting the right embryo will become even more important."
Dr Daniel Brison, co-director of the North West Embryonic Stem Cell Centre in Manchester, said: "The technique used by this, and other groups, of using infra-red spectroscopy to select embryos is very promising.
"I have high hopes that this, and or, other metabolic profile techniques will be used in clinics throughout the UK within the next two to three years.
"There is a very real need to improve our IVF success rates as at the moment four out of five attempts don't work.
"If we can get better at choosing the best embryo to implant then we can increase the efficiency of IVF, move towards single embryo transfers and thus reduce the risk to mothers and babies."
But he said further research was needed to confirm the test was useful.
He added: "It will be of most help to mothers who can produce a large number of embryos as there will be more options to choose from.
"Unfortunately it will be less beneficial for women, such as older mothers, who are only able to produce one or two embryos."