Scientists revealed the birth of a baby boy, now five months old, using DNA from three parents.
Fertility experts hailed the breakthrough as “great news and a huge deal” for the future of reproduction.
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 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 a “second” mother – an unknown female donor.
The aim was to replace defective mitochondrial DNA and prevent the disease being passed on through the maternal line.