Mitochondrial mutations can cause or contribute to a wide number of problems—including blindness, deafness, diabetes and neurological diseases. Many women give birth to a child who is sick with severe problems that turn out to be due to mitochondrial mutations. The parents then face a quandary: whether to risk having another child, knowing that the same disease can reoccur.

Scientists have been working to develop a way to replace a mother’s mutated mitochondria with healthy mitochondria, allowing the parents to have children who are healthy and survive. The children would have more than 99.99% of their DNA from their two parents and an infinitesimal fraction—less than 0.01%—from the woman who provided the healthy mitochondria. The procedure, called mitochondrial replacement therapy (MRT), could help hundreds of parents in the U.S., and thousands around the world.

But research on this potential lifesaving procedure has been blocked in this country, as in Britain. Last February the Food and Drug Administration held hearings and decided to delay trials of this therapy in humans until more research is done. Many physicians, scientists and patients unsuccessfully fought the FDA’s decision. They were right to do so. The decision should be revisited and overturned.