I can’t go any further without talking about the term we use to describe these children. Journalists, myself included, have called them “three-parent babies” because they are created using DNA from three people. Briefly, the approach typically involves using the DNA from the nuclei of the intended parents’ egg and sperm cells. That’s where most of the DNA in a cell is found.
But it also makes use of mitochondrial DNA (mtDNA)—the DNA found in the energy-producing organelles of a cell—from a third person. The idea is to avoid using the mtDNA from the intended mother, perhaps because it is carrying genetic mutations. Other teams have done this in the hope of treating infertility.
mtDNA, which is usually inherited from a person’s mother, makes up a tiny fraction of total inherited DNA. It includes only 37 genes, all of which are thought to play a role in how mitochondria work (as opposed to, say, eye color or height).
That’s why some scientists despise the term “three-parent baby.” Yes, the baby has DNA from three people, but those three can’t all be considered parents, critics argue. For the sake of argument, this time around I’ll use the term “three-person IVF” from here on out.
So, about these babies. The first were reported back in the 1990s. Jacques Cohen, then at Saint Barnabas Medical Center in Livingston, New Jersey, and his colleagues thought they might be able to treat some cases of infertility by injecting the mitochondria-containing cytoplasm of healthy eggs into eggs from the intended mother. Seventeen babies were ultimately born this way, according to the team. (Side note: In their paper, the authors describe potential resulting children as “three-parental individuals.”)
But two fetuses appeared to have genetic abnormalities. And one of the children started to show signs of a developmental disorder. In 2002, the US Food and Drug Administration put a stop to the research.