British women could be receiving a controversial "three-parent baby" treatment on the NHS as early as next spring.
An independent panel of experts has cleared away remaining safety hurdles to recommend "cautious adoption" of mitochondrial replacement therapy (MRT) for devastating inherited diseases.
The UK fertility regulator, the Human Fertilisation and Embryology Authority (HFEA), is now almost certain to give the final go-ahead for the treatments.
Scientists at the University of Newcastle, which has pioneered the treatments, say they already have women lined up for the therapy and are ready to apply for a licence to begin the procedures. The team hopes to treat up to 25 women a year with NHS funding.
Babies born after MRT would effectively have three genetic parents. A tiny proportion of their DNA would come from their mother, father and a third person, an egg donor. The aim is to replace abnormal genes in the mitochondria, rod-like power plants in cells that generate energy.
Mitochondria only hold around 0.1% of a person's DNA, which is always inherited from the mother and has no influence over individual characteristics such as appearance and personality. It is quite separate from the DNA in the cell nucleus which house the vast majority of an individual's genes.
But when mitochondrial DNA (mtDNA) goes wrong, the results can be catastrophic, leading to a wide range of potentially fatal conditions affecting vital organs, muscles, vision, growth and mental ability.
In theory, mitochondrial replacement can not only prevent a child developing inherited diseases, but also protect future generations.
Last year, the UK became the first country in the world to legalise mitochondrial replacement after MPs and peers voted in favour of allowing it.
The HFEA will consider the issue at a pivotal meeting on December 15, when it will decide whether clinics may make applications to offer the treatment. If it agrees with the scientists, the first women could undergo mitochondrial replacement therapy as early as March or April next year.
Dr Andrew Greenfield, who chaired the expert panel and is an HFEA board member, said: "We think that the cautious approach to the use of mitochondrial donation in treatment that we recommend strikes the right balance between offering access to this exciting new treatment to couples at real risk of having a genetically-related child with mitochondrial disease, while doing all we can to ensure that the treatment is safe and effective."
Robert Meadowcroft, chief executive of Muscular Dystrophy UK, which supports families affected by mitochondrial diseases, said: "We wholeheartedly support the positive recommendations for mitochondrial donation IVF to be cautiously implemented in clinical practice, for carefully selected patients.
"This pioneering technique could give women with mitochondrial disease the chance to have a healthy child, without the fear of passing on this condition which can lead to ... multiple disabilities and indeed life-limiting impairments.
"We are thrilled to see how the procedure has advanced and look forward to the possibility that it may shortly be available to eligible women at specialist clinics."
However, not everyone is in favour of women receiving the treatments.
Dr David Clancy, from the faculty of health and medicine at the University of Lancaster, said the technique was "currently imperfect".
He maintained that the risk of carry-over and reversion could lead to as many as one in 30 women receiving mitochondrial replacement therapy giving birth to a child with an inherited disease.
Dr Clancy said: "By the intervention that is MRT, the evidence now suggests that, at some point, producing a child who will suffer from mitochondrial disease is a certainty. Are we, as a society, okay with that?"