A baby boy has been born using a "three parent" technique that combines DNA from three individuals, researchers report.
The now-five-month-old was born to Jordanian parents, carried by a 36-year-old mother who had four pregnancy losses and two deceased children who had Leigh syndrome.
Leigh syndrome is a fatal disorder that breaks down the central nervous system, resulting in loss of motor skills and mental ability.
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The gene for the disease is found in DNA in the mitochondria, the powerhouse of a cell that provides energy. Mitochondrial DNA is inherited only from the mother.
Writing in the journal Fertility & Sterility, an international team of researchers described the first live birth using human ooyctes, or eggs, using a "three parent" technique.
To achieve conception, the mitochondrial DNA from the Jordanian mother was discarded and her nuclear DNA kept. That nuclear DNA was then added to a donor egg, which provided the mitochondrial DNA for the baby.
It was fertilized with the father's sperm.
Study co-author Dr. Taosheng Huang, of Cincinnati Children's Hospital Medical Center, treats patients with mitochondrial disease, which affects nearly every organ in the body.
Huang says he was "so excited" by the birth and what it could mean for other patients.
"They're so desperate. You feel hopeless for those people. You want to help them, but you don't know how to do it. So when I see this success story ... I think, that's great."
The procedure resulted in the first live birth of a boy following spindle nuclear transfer, the researchers said in a summary published by the journal. Scientists plan to make a fuller presentation at a meeting next month.
So far, everything seems perfect with the baby, who was born in New York City, Huang said. The baby's health will be closely monitored.
Dr. John Zhang, of the New Hope Fertility Center in New York, led the team, which performed the technique in Mexico, New Scientist magazine reported.
The technique is not approved in the United States, but Zhang told the magazine: "To save lives is the ethical thing to do."
This particular procedure would violate a Canadian law, said Dr. Neal Sondheimer, a physician at SickKids Hospital in Toronto who researches mitochondrial mutations in diseases.
"I think we need to reflect on the original intent of the law passed in 2004 governing reproductive cloning to see if it still fits, in light of the ability to do this procedure and to allow people to have healthy children," Sondheimer said.
Last year, the U.K. Parliament approved a different three-parent technique for Mitochondrial Replacement Therapy in clinical trials.
An earlier technique from the 1990s involved adding healthy mitochondria from a donor to an affected woman's egg. Dozens of children were born, but many still developed genetic disorders and the procedure was stopped.