The world's first three-parent baby has been hailed as "a huge deal" for the future of reproduction. Scientists yesterday revealed the birth of a baby boy, now five months old, using DNA from three parents.Fertility experts hailed the breakthrough as "great news" for the future of reproduction, but expressed concern that it was achieved only because US scientists crossed over to Mexico to take advantage of lax regulation.The child was born to a couple from Jordan who had been trying to start a family for almost 20 years. His mother carries genes for Leigh syndrome, a fatal disorder that affects the developing nervous system and which caused the deaths of their first two children.The baby was conceived from an egg containing nuclear DNA from his mother and father and mitochondrial DNA from an unknown "second" mother to replace defective DNA and prevent the disease being passed on.A pioneering approach called spindle nuclear transfer enabled the breakthrough birth.Scientists from New Hope Fertility Centre in New York, led by John Zhang, created five embryos using the technique. One developed normally and was implanted.The method has not been approved in the US, so Zhang went to Mexico where he said "there are no rules". Defending his decision, he said: "To save lives it is the ethical thing to do."Dusko Ilic, a reader in stem cell science at King's College London, said: "This is great news and a huge deal - it's revolutionary."But experts said they were concerned about the lack of regulation in Mexico and it was crucial that the child's health was closely monitored. ..