A new report has made it more likely that babies with three genetic parents could be born in the UK to prevent devastating inherited diseases.
The panel appointed by regulators the Human Fertilisation and Embryology Authority (HFEA) concluded that the controversial IVF technique developed at Newcastle University was “potentially useful” and did not appear to be unsafe.
But it added there was still more research to be done - some of it “critical” - before such treatment should be offered.
Fertility rules were changed by the Government in February paving the way for Britain becoming the first country in the world to allow mitochondrial replacement (MR) therapy.
A final decision to allow the treatments will need the approval of both houses of Parliament but could come as early as next year. Mitochondria are tiny powerhouses in cells that generate energy and have a small amount of their own DNA, separate from the bulk of the human genetic code.
Defects in mitochondrial DNA (mtDNA) are responsible for a host of inherited diseases, including conditions leading to muscle wasting, heart problems, loss of vision, organ failure and epilepsy.
MR treatment, which employs two different IVF techniques, aims to prevent these diseases by giving babies healthy mtDNA from donor eggs.
The baby is born with normal “nuclear” DNA passed down by its parents - containing most inherited traits such as eye and hair colour and height - plus a tiny amount of mtDNA donated by a second donor “mother”.
In effect the baby has three genetic parents, though the donated mtDNA contains less than 1% of its genes.
Since the healthy mtDNA would be inherited by future generations, the treatment has the potential to eradicate mitochondrial diseases from affected families.
Critics argue that allowing the treatments could be the first step down a slippery slope towards “designer babies” and eugenics.
If mitochondrial replacement is permitted, more than 100 “three-parent” babies could be born in the UK each year.
The new expert review, the third published, was requested by the Department of Health and forms part of a broader process of consultation.
HFEA chairwoman Sally Cheshire said: “The review process has assembled an evidence base on the safety and efficacy of these two mitochondrial replacement techniques which stands comparison with anything published in the UK or abroad.
“The science is complex, but the aim is simple: to enable mothers to not pass on to their children a range of serious, and sometimes fatal, inherited conditions. In all of our discussions we should not lose sight of this.
“Now it is a question for others. If the Government decides to seek to change the law they will need the approval of both Houses of Parliament, and it is only right that they consider all the ramifications, social as well as medical, before they make up their minds. There is a long way to go yet.”
Reacting to the report, Professor Doug Turnbull, who has led the research at Newcastle University, said: “It is very encouraging that this respected and independent group of scientists have concluded that the techniques would be useful to prevent serious mitochondrial DNA disease and the evidence shows that they are not unsafe. Further work is needed and it is even more important that Parliament is able to decide whether these techniques should be allowed in the UK.”