Britain鈥檚 fertility regulator on Wednesday confirmed the births of the U.K.鈥檚 first babies created using an experimental technique combining DNA from three people, an effort to prevent the children from inheriting rare genetic diseases.

The Human Fertilization and Embryology Authority said fewer than five babies have been born this way in the U.K. but did not provide further details to protect the families鈥� identities. The news was first reported by the Guardian newspaper.

In 2015, the U.K. became the first country to adopt regulating methods to help prevent women with faulty mitochondria 鈥� the energy source in a cell 鈥� from passing defects on to their babies. The using the technique was reported in the U.S. in 2016.

The genetic defects can result in diseases such as muscular dystrophy, epilepsy, heart problems and intellectual disabilities. About one in 200 children in Britain is born with a mitochondrial disorder. To date, 32 patients have been authorized to receive such treatment.

For a woman with faulty mitochondria, scientists take genetic material from her egg or embryo, which is then transferred into a donor egg or embryo that still has healthy mitochondria but had the rest of its key DNA removed.

The fertilized embryo is then transferred into the womb of the mother. The genetic material from the donated egg comprises less than 1% of the child created from this technique.

鈥淢itochondrial donation treatment offers families with severe inherited mitochondrial illness the possibility of a healthy child,鈥� the U.K. fertility regulator said in a statement Wednesday. The agency said it was still 鈥渆arly days鈥� but it hoped the scientists involved, at Newcastle University, would soon publish details of the treatment.

Britain requires every woman undergoing the treatment to receive approval from the Human Fertilization and Embryology Authority. The regulator says that to be eligible, families must have no other available options for avoiding passing on genetic disease.

Many critics oppose the , arguing there are other ways for people to avoid passing on diseases to their children, such as egg donation or screening tests, and that the experimental methods have not yet been proven safe.

Others warn that tweaking the genetic code this way could be a slippery slope that eventually leads to designer babies for parents who not only want to avoid inherited diseases but to have taller, stronger, smarter or better-looking children.

Robin Lovell-Badge, a stem cell expert at the Francis Crick Institute, a biomedical research center in London, said it would be critical to monitor the babies鈥� future development.

鈥淚t will be interesting to know how well the (mitochondrial donation) technique worked at a practical level, whether the babies are free of mitochondrial disease and whether there is any risk of them developing problems later in life,鈥� he said in a statement.

Scientists in Europe published research earlier this year that showed in some cases, the small number of abnormal mitochondria that are inevitably carried over from the mother鈥檚 egg to the donor鈥檚 can reproduce when the baby is in the uterus, which could ultimately lead to a genetic disease.

Lovell-Badge said the reasons for such problems were not yet understood and that researchers would need to develop methods to reduce the risk.

to create babies from three people, including an egg donor, found that years later the children were doing well as teenagers, with no signs of unusual health problems and good grades in school.

Doctors in the U.S. were the first to announce the world鈥檚 first baby using the mitochondria donation technique, after the treatment was conducted in Mexico.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute鈥檚 Science and Educational Media Group. The AP is solely responsible for all content.

Maria Cheng, The Associated Press