A new approach to embryo assessment could help IVF fertility experts understand why so many apparently healthy embryos are not viable.
Scientists working on the study believe that combining chromosome analysis and mitochondrial assessment on a five-day embryo could offer the most accurate and predictive measure of embryo viability, which would in turn improve IVF outcome.
Dr Epida Fragouli from Reprogenetics UK and the University of Oxford’s Nuffield Department of Obstetrics and Gynaecology in Oxford, UK, told delegates at the annual meeting of European Society Of Human Reproduction And Embryology (ESHRE) in Helsinki, Finland, that her study “demonstrates that mitochondrial DNA levels are highly predictive of an embryo’s implantation potential”.
Even embryos that are chromosomally normal and have a good morphological appearance under the microscope are unlikely to produce a baby if they have unusually high levels of mitochondrial DNA, she said.
She said the evidence is growing after a prospective study of 280 blastocysts that were tested to be chromosomally normal.
It is the first study to evaluate the predictive power of mitochondrial DNA quantification with a prospective, blinded, non-selection design, which means the mitochondrial DNA levels of the blastocysts were not known at the time of transfer.
Of the 111 single blastocyst transfers whose outcome was so far known, 78 (70%) led to ongoing pregnancies, and all had normal levels of mitochondrial DNA.
The remaining 33 blastocysts failed to implant, and eight of these (24%) had unusually high levels of mitochondrial DNA.
“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,” said Dr Fragouli, who added that the results were “very robust”.
Mitochondrial DNA levels can be simply and quickly measured by a polymerase chain reaction (PCR) strategy, but next generation sequencing (NGS) can also be used, she said.
However, all embryos must first be screened for aneuploidy and that the mitochondrial DNA test is only applicable to chromosomally normal embryos.
“Aneuploidy is still the biggest cause of embryo implantation failure, so mitochondrial analysis does not replace that,” she said.
“It is the combination of the two methods – mitochondrial DNA testing and chromosome analysis – that are so powerful.”
The group has started offering mitochondrial DNA quantification clinically in the USA, and has applied to the HFEA for a license for use in the UK.
* The conference also heard that three in four women who start fertility treatment will have a baby within five years – either naturally or through treatment.
A large cohort study, which analysed the birth records of almost 20,000 women having fertility treatment in Denmark between 2007 and 2010, found that 57% had their baby because of the treatment, while 14% conceived naturally. More than half (57%) gave birth within two years.
Dr Sara Malchau of Copenhagen University Hospital, Hvidovre, Denmark, said: “We are now able to provide couples with a reliable, comprehensible, age-stratified long-term prognosis at start of treatment.”
Leave a Reply