• The world's first "three-parent baby" has been delivered by a US medical team in Mexico.
• The three-person baby technique lets parents with genetic mutations have a healthy baby
• The technique is only legal in the United Kingdom, but this is the first birth
• The parents are from Jordan
• The mother carries a fatal genetic mutation, her two first kids died by age 6
• A New York team carried out the egg-editing procedure in Mexico where there are no rules against the procedure
• 'This is a milestone,' lead surgeon Dr John Zhang told Daily Mail Online
• He said in the future this technique could be 'unlimited' - from helping older women give birth, to editing a child's appearance or skills
The world's first child has been born using a revolutionary technique that combines the genes of three parents.
The five-month-old 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 that could kill him.
The controversial technique has only been legally approved in the UK.
But the first baby was engineered by a US medical team who treated the parents in Mexico, where there are no laws to block the procedure.
And embryologists believe the 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," said Dr John Zhang, who led the medical team from New York City's New Hope Fertility Centre.
The technique could be used for anything - from avoiding disease to altering a baby's appearance, but for now, disease is the focus.
The world's first "three-parent" baby was created to prevent him inheriting a genetic condition his mother carries in her mitochondria.
The disease - Leigh's syndrome - would have killed him within a few years.
How is the procedure done?
1. Take eggs from a mother with damaged mitochondria.
2. Take eggs from a donor with healthy mitochondria.
3. Remove and save the nucleus from the mother's egg. This contains the majority of her genetic material.
4. Remove and discard the donor's nucleus.
5. Place the mother's nucleus in the donor's egg with the healthy mitochondria.
6. The egg can then be fertilised by the father's sperm.
"It proves for the first time that genetic information from three people can avoid disease," Zhang said.
"We now know reconstitution of human eggs can produce a healthy baby.
"No other technique has been established."
Dr Zhang revealed some details about the family's devastating journey to reach this world-first.
The parents have already lost two children to Leigh's syndrome, their first at the age of 6; their second at 8 months.
Leigh's syndrome is a severe neurological disorder that attacks the nervous system.
It gradually inhibits a child's mental and physical abilities from the moment they are born.
Sufferers typically die by the age of 3 of lung failure.
Tests revealed that the boy's mother carries genes for the disease in her mitochondria.
Devastated by the loss of their two children, the couple flew to America to meet Zhang at New Hope, which focuses on training in new innovations.
Because of the strict regulations in the United States, the team sought the nearest country without legislation to block them. That was Mexico.
The boy was born through a technique called spindle nuclear transfer.
Zhang removed the nucleus from one of his mother's eggs. It was then inserted in a donor egg that had its nucleus removed.
This egg was then fertilised with sperm from the father.
Five eggs were created with this technique, only one of which survived. The findings will be showcased at the American Society for Reproductive Medicine's Scientific Congress in Salt Lake City next month.
The technique was carried out in Mexico because it would not be approved in the US by regulators.
Echoing both the fears and excitement of the entire medical community, Zhang pointed out: "This is just the start."
For now, embryologists are focusing on the technique as a way to avoid hereditary diseases that prevent many adults with genetic mutations from having children.
Down the line, however, Dr Zhang said its application could be "unlimited", even to the point of altering an unborn child's DNA to edit their appearance or skill set.
"It's all possible. It just depends how you use the technique.
"This technique is a new platform. How far it can go, I really cannot imagine. But it's totally possible to accomplish [cosmetic editing].
"As with any development of new techniques, you always need to bear in mind efficacy and safety. Even with IVF."
Professor Simon Fishel, Founder and President, Care Fertility Group, and Professor of Human Reproduction, said: 'This is a devastating disease that we do not wish children to be born with, and what's more, we would wish to eradicate from any family lineage - and this technology will help achieve this.
"However, any first-time medical procedure moving from successful animal studies to the human, that will take several years until we understand its impact, is a necessary experimental step forward, which we hope and believe should be totally safe and utterly effective.
"Congratulations to this team and all those hoping to help these unfortunate families; and we should proceed with caution and due regulation."