Like all humans, the five-month-old boy carries DNA from both his parents. But he also has a tiny piece of genetic code from a donor.
It means he has avoided inheriting a genetic condition from his Jordanian mother, known only as IS, that could kill him. The controversial technique has only been legally approved in the UK.
However, the first baby was engineered by a US medical team who treated IS and her husband in Mexico, where there are no laws to block the procedure.
And embryologists believe this birth should fast-forward progress around the world, offering hope to millions who face the prospect of delivering terminally ill children.
'This is a milestone technique,' Dr John Zhang, who led the medical team from New York City's New Hope Fertility Center, told Daily Mail Online.
'It proves for the first time that genetic information from three people can avoid disease,' he said.
'We now know reconstitution of human eggs can produce a healthy baby.
'No other technique has been established.'