A baby boy with three biological parents was just born after being conceived in Mexico.
The infant came into the world thanks to a technique that involves manipulating the genetic material from two mothers before fertilizing the resulting egg with the father’s sperm. Variants of the process have been shunned by regulators in the U.S. despite the chance that they could help parents-to-be avoid passing down some rare genetic disorders.
The doctor who led the work, John Zhang of the New Hope Fertility Center in New York, used a process called spindle nuclear transfer to swap parts of the nuclei of five eggs from the boy’s mother into donor eggs before injecting sperm. Four of the five eggs began to grow, but only one developed normally.
The goal of the work is to allow mothers carrying genetic mutations that cause mitochondrial diseases, which afflict 1,000 to 4,000 people in the U.S. each year, to give birth to healthy babies. In the case of the couple that Zhang’s team worked with, the mother carries genes for Leigh syndrome, which is fatal. Before giving birth to her son in April, she had already had four miscarriages and two children who died of Leigh syndrome.
According to an interview in New Scientist, which first reported the story, Zhang said that U.S. regulations drove his team to move the procedure to Mexico—where, he said, “there are no rules.”
If such a statement sounds cavalier, outside scientists who commented on the work suggested that the team behaved ethically. The researchers made sure the baby was male to eliminate the possibility that mitochondrial DNA from the donor egg, which would be passed down through the maternal lineage, would not be inherited by any future generations.
This isn’t the first time a child has been born with three parents; the practice dates to the 1990s. In 2000 a girl was born whose parents used a different technique to conceive her, but it was shut down by the FDA the shortly thereafter. A similar process to the one Zhang used has been approved in the U.K.
For his part, Zhang has a history of working on the cutting edge of reproductive medicine. Over a decade ago, he implanted embryos with genetic material from three parents into a woman in China, and triplets began to grow. All three died before birth, but doctors at the time felt they might’ve made it if the woman had access to the better medical care available in the U.S.