Britain's leading bioethics council has given the green light to a controversial fertility treatment that results in the child having genes from a mother, father and from a female donor.
The technique is intended to prevent life-threatening disorders being passed from mother to child. But the decision could now open the way for the world's first three-parent children.
"There are women who carry mutations in their mitochondrial DNA, the result of which is that they have children who at some stage - and it can be late in life - develop really quite severe disorders, hearts disease, lung, kidney disease etc," Hugh Whittall, Nuffield Bioethics Council director, says.
"If they can be freed of the risk of passing on those diseases, they can be sure that they will have healthy children and that their children will know that this is no longer in the family to be passed on from one to the next."
The genetic techniques involve taking DNA material - just 0.1 per cent of the chromosome - from another woman’s egg. This is then used to repair the faulty DNA in the mother's egg.
Having done that repair, the egg is then fertilised and, the woman then follows a normal fertility treatment.
Crucial ethical line
Opponents say the in vitro fertilisation techniques are dangerous and unnecessary and set a precedent for taking the methods further.
"It's one step away from genetically engineering of human babies and it creates a precedent for doing that because it crosses the crucial ethical line that ethicists have maintained for the last 20 or 30 years, which is to not interfere with the human genome, with human DNA." David King, director of Human Genetics Alert, says.
But Dr Geoff Watts, the Chair of the Nuffield Council's inquiry into the potential treatments, says it is only endorsing the use of the methods in very limited circumstances.
"We are only talking about the use of these techniques in the clearly-defined situation of otherwise incurable mitochondrial disorders, under strict regulation," he says.
Those behind the report say a child produced using these methods will still look like their main parents, and the donor should not be regarded legally or ethically as a parent.
The techniques still need to be proven to be safe and effective. But if they are, they will give women with genetic disorders, their only chance of having their own healthy children.