Doctors in the United Kingdom have used a new method to help mothers have healthy babies without mitochondrial diseases. The study was shared on July 16, 2025, in the New England Journal of Medicine. Mitochondrial diseases are serious problems that come from damaged parts of cells called mitochondria. These diseases can cause muscle problems, seizures, organ failure, and sometimes fatality. The new method is called mitochondrial replacement therapy. It stops mothers from passing these diseases to their children. The United Kingdom approved this method in 2016. Australia also allows it, but many countries, like the United States, do not.

Scientists used this method with 22 patients. So far, eight healthy babies were born without mitochondrial diseases. One more pregnancy is still happening. The method works by putting the mother’s DNA into a healthy egg from another woman. The egg from the donor has good mitochondria. The donor’s DNA is removed. The baby gets DNA from three people: the mother, the father, and the donor. But the donor’s DNA is very small—less than 1%. Scientists say the baby will not look like the donor. Some experts worry about possible problems in the future.