British parliamentarians have voted in favor of legalizing a form of IVF that would create babies from the biological material of three individual people.
The "free vote" — allowing MPs to vote using personal conscience rather than along party lines — passed in the House of Commons Tuesday with 382 votes in favor of the measure and 128 against. Those who voted "yes" included Chancellor of the Exchequer George Osborne and Prime Minister David Cameron. The House of Lords will now consider the measure.
"We're not playing god here," Cameron said, "we're just making sure that two parents who want a healthy baby can have one."
Britain could soon be the first nation in the world to perform the controversial technique aimed at halting genetic diseases being passed from mother to baby through the mitochondrial donation of another woman.
Addressing the assembled politicians, Health Minister Jane Ellison declared the vote "a bold step for parliament to take, but it is a considered and informed step."
"This is world-leading science within a highly respected regulatory regime," she said. "And for the many families affected, this is light at the end of a very dark tunnel."
Ellison also dismissed fears that the move is the beginning of a "slippery slope" towards so-called designer babies, noting that the same concerns had been raised when IVF was legalized, and those fears hadn't materialized.
If the House of Lords votes to approve the measure and it passes into law, the first such baby could be born as early as 2016.
The method involves replacing a mother's defective mitochondria with the healthy mitochondria of a donor woman, preventing the passing down of mitochondrial disease, which can lead to brain damage, muscle wasting, heart failure and blindness. Mitochondria are tiny compartments found within almost all body cells that have a number of functions, including converting energy from food to energy the body can use. Defective mitochondria can only be passed down through the mother.
Mitochondrial replacement therapy would mean babies would acquire only 0.1 percent of their DNA from the second woman — far less than the amount of DNA transferred through blood transfusion or organ donation. The procedure would also create a permanent change: the genetic disease would not recur again in future generations.
Advocates say around 150 babies could be saved from deaths caused by mitochondrial disease each year using the technique.
But the move to introduce laws allowing the procedure has been met with some opposition, including from religious figures.
"Changing the human germline represents an ethical watershed; it is right to be cautious," Dr. Brendan McCarthy, the Church of England's national adviser on medical ethics, said in a statement.
McCarthy added that while the Church of England has great sympathy for families affected by mitochondrial disease, there were a number of scientific and ethical questions that need to be answered and, "the law should not be changed until there has been further scientific study and informed debate into the ethics, safety and efficacy of mitochondrial replacement therapy."
Conservative MP Jacob Rees-Mogg echoed those fears on BBC's Today program, saying that the vote was a step towards creating genetically engineered babies.
"At the moment there is a very clear boundary that babies cannot be genetically altered," Rees-Mogg said. "Once you've decided that they can, even for a small number of genes, you have done something very profound, and then it's merely a matter of degree as to what you do next."
But others have praised Tuesday's vote, among them Gillian Lockwood, a reproductive ethicist and medical director at the Midland Fertility Clinic, who told VICE News that she found it encouraging that the vote had passed by such a convincing majority.
"It suggests that [the MPs] have come down on the side of compassion and haven't been taken in by the scare stories," she said.
Lockwood, who has worked in fertility medicine since 1991, said that she has looked after some babies with mitochondrial disease and that she had a clear "sense of the permanent state of sorrow and distress their parents were in, knowing that [their children] would be apparently born healthy, but often very, very rapidly would go into a decline and die."
"With most genetic diseases, there's a chance that you could have one child that will be affected and another one that won't be," Lockwood said. "If it's mitochondrial disease, it's the case that all children will be affected. This is quite a small number of people, but the extent to which they're affected can be absolutely devastating."
Lockwood added that it would be reassuring for parents to "have children knowing that they're going to have long and healthy lives," and denied the argument that these couples wanted designer babies.
"Half of all babies get made by accident, and a significant proportion of the others get made by a combination of moonlight and roses," she said. "A very small proportion — one in six — need help from doctors like me, but [the couples] just want a baby. A happy, healthy baby is all they want."
Follow Sally Hayden on Twitter: @sallyhayd