Britain's fertility regulator on Thursday granted doctors the first UK license to create babies using a three-parent IVF technique designed to prevent inherited genetic diseases.
The license, granted to a team of doctors in Newcastle, northern England, means the first child created in Britain using the mitochondrial pronuclear transfer technique could be born before the end of this year.
Critics of the treatment say it is a dangerous step that will lead to the creation of genetically modified "designer babies". But the medical team at the Newcastle Fertility Centre said they were delighted with the decision "to help families affected by these devastating diseases".
"Many years of research have led to the development of pronuclear transfer as a treatment to reduce the risk of mothers transmitting disease to their children," said Mary Herbert, a professor of Reproductive Biology at the Centre.
"It's a great testament to the regulatory system here in the UK that research innovation can be applied in treatment."
The technique involves intervening in the fertilization process to remove mitochondria, which act as tiny energy-generating batteries inside cells, and which - if faulty - can cause fatal heart problems, liver failure, brain disorders, blindness and muscular dystrophy.
The treatment is known as "three-parent" IVF because the babies, born from genetically modified embryos, would have DNA from a mother, a father and from a female donor.
It is designed to help families with mitochondrial diseases - incurable conditions passed down the maternal line that affect around one in 6,500 children worldwide.
Britain's parliament voted last year to change the law to allow the treatments if and when they were ready for licensing.
But the regulator, the Human Fertilisation and Embryology Authority (HFEA), still had to approve each clinic and each patient on an individual basis before the treatment can be carried out.
Fertility specialists welcomed Thursday's decision. Simon Fishel, managing director of CARE Fertility, said it was "excellent news" and "a milestone that all who care about medical health will welcome".
Allan Pacey, a fertility expert at Sheffield University, said it was "a great day for science".
While Britain has been at the forefront of scientific advances and ethical debate about pro-nuclear transfer techniques, it will not be the first country in the world to have children born using 3-parent IVF treatment.
The world's first and so-far only known mitochondrial transfer baby was born in 2016 after U.S. doctors working at a clinic in Mexico helped a Jordanian couple conceive using the treatment.