Combining two fertility tests could boost IVF success rates, the largest study of its kind suggests.
New data from the University of Oxford shows that examining mitochondrial DNA and also looking at chromosomes for signs of problems gives a highly accurate picture of whether fertility treatment could be a success.
Experts have been looking at how mitochondria - which are crucial for the development of healthy babies - behave inside each embryo.
They know 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.
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 combined test involves usual chromosomal screening then looking closely at why the remaining embryos are still not resulting in a baby.
In the new study, 280 embryos grown in the laboratory for five or six days were found to be chromosomally normal.
Of these, 111 were put into women and 78 (70%) led to ongoing pregnancies.
All those that resulted in pregnancy had levels of mitochondrial DNA known to be normal, but of the remaining 33 blastocysts that failed to implant, eight (24%) had unusually high levels of mitochondrial DNA.
Experts said it was "highly statistically significant" that none of the embryos with too high levels of mitochondrial DNA implanted.
Dr Epida Fragouli, from Reprogenetics UK and the University of Oxford's Nuffield Department of Obstetrics and Gynaecology, said the study "demonstrates that mitochondrial DNA levels are highly predictive of an embryo's implantation potential".
She added: "The results confirm that embryos with elevated levels of mitochondrial DNA rarely implant and support the use of mitochondrial quantification as a marker of embryo viability."
Chromosomal abnormality is still the main reason why embryos do not implant so experts hope that combining the two tests will boost IVF results.
The research was presented at the European Society of Human Reproduction and Embryology conference in Helsinki.
The test is already being offered in the US, and fertility regulator the Human Fertilisation and Embryology Authority is considering whether it should be allowed in the UK.
Previous research by Professor Dagan Wells from Oxford found that women undergoing IVF could have an 80% chance of success thanks to the mitochondrial DNA test.
Only around a third of IVF transfers in the UK are successful.
A clinical trial carried out in New York on mitochondrial DNA has resulted in a pregnancy success rate of around 80%.