The first three-parent baby in the world has been born, reports New Scientist. The baby boy, now five months old, has been born from a controversial new technique that uses DNA from three parents: his father, mother and egg donor.

The goal of this technique, which is described in the journal Fertility & Sterility, is to prevent the child from inheriting a deadly genetic disease called Leigh syndrome from his mother, who apparently lost two babies previously. As of now, the technique is only legal in the UK, but scientists hope this could one day transform reproduction.

The Jordanian parents of the three-parent baby could not conceive for almost two decades. They decided to approach experts led by John Zhang at the New Hope Fertility Center in New York.

The team removed the nucleus from one of the mother’s eggs, leaving the disease-causing DNA, and inserted it into the donor egg, which had its own nucleus extracted. The egg, which now has both the DNA from the mother and the donor, was then fertilized by the father’s sperm.

The procedure was conducted in Mexico but it was not stated where the three-parent baby was born.  The team is expected to present the procedure in Salt Lake City next month.

Other fertility experts call this procedure revolutionary. However, some have criticized the scientists’ decision to perform the technique, calling the team unethical and irresponsible.

“It is outrageous that they simply ignored the cautious approach of US regulators and went to Mexico because they think they know better,” says David King, director of Human Genetics Alert. “These scientists have used an experimental technique that many scientists still think is unsafe in order to create a world first.”

This view is shared by Bert Smeets, director of the Genome Centre at Maastricht University, the Telegraph reports. However, Zhang argues that their work is not unethical and saving lives is the ethical thing to do.

Moreover, Zhang says this is just the start. The technique could be used to a number of applications, including changing a child’s DNA to alter his appearance.