Scientists have developed a test they hope could significantly increase the chances of successful IVF treatment.
Many embryos do not develop to full term
The test can predict with around 60% accuracy whether an embryo is likely to produce a successful pregnancy.
At present only about 30% of women become pregnant after one round of IVF treatment.
Details of the test, developed by the Sher Institutes for Reproductive Medicine, will be published in the Journal of Reproductive Biomedicine.
The test samples the fluids around an embryo for the presence of a genetic marker called sHLA-G.
The researchers have found that only embryos which produce sHLA-G in sufficient concentration are likely to be viable.
In trials on 201 women, the test produced a 70% accuracy level in women under the age of 39, and 50% in women aged 39 to 44.
Cutting multiple births
Lead researcher Professor Geoffrey Sher said the test may allow doctors to cut the number of embryos they use in IVF treatment - and thus reduce the number of multiple births.
He said: "Ever since the birth of the first test tube baby in 1978, the desire to optimise pregnancy rates has prompted many IVF specialists to transfer more rather than fewer embryos - keeping their fingers crossed that only one will attach to the uterine lining.
"The unfortunate by-product of such practice has been the alarming incidence of IVF-related high-order multiple pregnancies (triplets or greater) with serious incumbent risks to both the mother and her babies."
"The discovery, that sHLA-G is expressed in high concentrations only by those embryos that are most likely to produce a pregnancy, brings IVF practitioners much closer to the long-awaited objective of 'one embryo, one healthy baby'."
The researchers believe that sHLA-G appears to protect the developing embryo from attack by the mother's immune system.
On occasion, the immune system is primed to attack the embryo because it contains genetic material from the father, which can be interpreted as foreign.
The researchers believe the new test will also determine whether a patient unlikely to conceive through IVF before an attempt is ever made.
A spokeswoman for the Human Fertilisation and Embryology Authority told BBC News Online: "Our policy is to encourage a reduction in the number of embryos that are transferred during treatment.
"Any technique, having gone through appropriate clinical trials, which is shown to increase a woman's chance of becoming pregnant could mean a move towards single embryo transfer.
"This would be good for a mother and good for her baby."
Under current rules in the UK, only two embryos can be transferred in any single round of IVF treatment on women aged under 40.
For older women, doctors have licence to use three embryos per treatment in exceptional circumstances.
Dr Mohammed Taranissi, director of London's Assisted Reproduction and Gynaecology Centre, said: "It is a very good idea, and if it adds another parameter to those we already use to select embryos, then it will be very useful."
However, Dr Taranissi said at this stage it was unclear whether the test would prove to be any more effective than selecting embryos based on how well they appeared to be dividing under the microscope.