Scientists have revealed the procedure of a pioneering IVF technique that enabled the birth of world's first three-parent baby last year, giving hope to families with inheritable mitochondrial disorders.

In the study, published in the journal Reproductive BioMedicine Online (RBMO), the researchers describe the procedure of mitochondrial replacement therapy (MRT) which helped in the birth of a healthy baby boy who was a carrier of Leigh Syndrome -- a progressive, fatal and genetic neurological disorder caused by a mutation in the mother's mitochondrial DNA.  The boy, born to a Jordanian couple, has the usual DNA from his parents, and a small amount of genetic code from a donor. 

"Thirty years ago it was discovered that certain rare diseases are associated with abnormal, mutated mitochondria in human cells. Ten years after that initial discovery, egg microsurgery enabled IVF specialists to change the cytoplasm including mitochondria from patients who had failed IVF multiple times," said Jacques Cohen, director of the ART Institute of Washington, Virginia. 

"Now, for the first time, an egg with abnormal mitochondria can be changed to contain mostly normal mitochondria from a healthy egg donor. This is a major change of technology and an obvious advantage for women who are at risk of passing such diseases on to the next generation," added Bart Fauser, professor and editor-in-chief of RBMO. 

Using an electrofusion technique, the researchers transferred the nuclear genome from the mother's egg (while leaving behind most of the mother's mitochondria) to the cytoplasm of a donor egg containing only healthy mitochondria. This egg was then fertilised by the father's sperm and transferred to the mother's womb and a baby boy was born at 37 weeks after an uneventful pregnancy. 

The announcement of the birth of the first baby born using MRT was met with mixed reactions in the media and will continue to generate debate surrounding the technique throughout the world, paving the way for changes in the law and regulation, the researchers noted.