Scientists have found a way of swapping the diseased DNA with healthy genetic material to treat an unborn child with a congenital disability, creating embryos free of mitochondrial disease.
Dozens of human embryos with three parents have been created by British scientists, ushering in an era of designer babies.
The embryos - which effectively have two mothers and one father - have been genetically engineered to be free from incurable muscle, brain, heart, and digestive illnesses, some of which kill within hours of birth.
The Newcastle University researchers say that within three years, it could allow women whose families are blighted by disease the chance of bringing a healthy child into the world.
The research centers on mitochondria - powerhouses inside cells that turn food into energy used by the brain and body.
'THIS WOULD BE AMAZING
Sharon Bernardi has suffered the heartbreak of witnessing six of her children die of mitochondrial disease within hours of birth.
She also had three miscarriages, and her only living child, Edward, 20, uses a wheelchair and needs round-the-clock care.
Sharon Bernardi
Miss Bernardi, of Sunderland, inherited diseased mitochondria from her mother, who lost three babies to Leigh's disease, which causes difficulties in swallowing and breathing.
Edward was four-and-a-half when he was diagnosed and was not expected to live past five.
Few of those with the condition survive past their teens. Miss Bernardi, 44, who cares full-time for her son and has been with her partner Neil Smith for 12 years, said: 'I wasn't diagnosed until after my fifth baby had died, no one knew why it was happening, they had no answers.
'I would get pregnant again and just pray it would be different that time.
'My Mum sat me down and told me it had happened to her. The previous generation lost 11 children in total.
'It is devastating, but I feel lucky to have Edward. It will be too late for me, but it would be amazing if scientists and doctors could prevent this in the future.'
Each mitochondrion has its DNA and is passed down from mother to child.
Severe defects in this DNA affect one in 6,500 babies and cause around 50 genetic diseases, some of which kill in infancy.
With no cure for the conditions, which include some forms of diabetes, blindness, and heart problems, women carrying diseased mitochondria often face the heartbreaking choice of whether it would be kinder to remain childless.
Scientists have found a way of swapping the diseased DNA with healthy genetic material, creating embryos free of mitochondrial disease.
The 'transplant' technique, described in the journal Nature, involves using IVF techniques to fertilize an egg from a healthy donor.
When the resulting embryo is just a few hours old, the nuclear DNA, or genes, from the sperm and egg are removed, leaving the healthy mitochondria behind.
The would-be mother's egg is then fertilized with her partner's sperm, and the nuclear DNA is removed and put into the donor egg.
This creates an egg where the genetic material comes overwhelmingly from the prospective parents, and the mitochondria are healthy.
If the method is successful, the disease should be eradicated from future generations of the family.
Professor Alison Murdoch, head of the Newcastle Fertility Centre, whose patients donated eggs for the study, said: 'It would be hype to say we are going to get rid of mitochondrial disease, but I think it's realistic to say you could get rid of it in an individual family.'
Eighty embryos were created in the Newcastle labs, each effectively with three parents - two mothers and a father.
A fourth parent - the man whose sperm was used to fertilize the donor egg - was involved, but none of his DNA was passed on.
Some embryos lived for six days before being destroyed to comply with fertility laws forbidding such embryos from being implanted in a woman.
But updated fertility laws which came into effect last year, leave the door open for the legislation to be amended quickly.
Lead researcher Professor Doug Turnbull said if this happened, the first babies could be born in as little as three years.
He said: 'This is a fascinating development with immense potential to help families at risk from mitochondrial diseases.'
I support Three parent babies solely because this can save lives, it's like organ donation, and this is the best course of action if we don't want an abortion, which I disagree with, because if we wish babies with disabilities to be able to live past birth while having a healthy life, then this is the option to cure those disabilities.
In the Netherlands, they're letting people let their children die because their children have chronic diseases, people are talking about abortion and assisted suicide, people are euthanizing these kids and, in some countries, in the cruelest ways against their will, and the same people euthanizing them in those countries are the ones discriminating against them and helping them suffer, this should be fully aloud and a skill to be honed.