LONDON — Britain's fertility regulator has approved controversial techniques allowing doctors to create babies using DNA from three people — what it called a “historic” decision to help prevent a small number of children from inheriting potentially fatal diseases from their mothers.

The regulator's chair, Sally Cheshire,?on Thursday described it as a “life-changing” moment for families who might benefit from the treatment.

“Parents at very high risk of having a child with a life-threatening mitochondrial disease may soon have the chance of a healthy, genetically related child,” she said in a statement.

The new procedures are intended to fix problems linked to mitochondria, the energy-producing structures outside a cell's nucleus.

Faulty mitochondria can result in conditions including muscular dystrophy, major organ failure and severe muscle weakness.

Last year, Britain changed its law to permit scientists to modify eggs or embryos before they are transferred into women, becoming the first country to legally approve the techniques.

In September, U.S.-based doctors announced they had created the world's first baby using such techniques, after traveling to Mexico to perform the methods, which have not been approved in the United States.

To help women with mitochondria problems from passing them down to their children, scientists remove the nucleus DNA from the egg of a prospective mother and insert it into a donor egg from which the donor DNA has been removed. That can happen before or after fertilization.

The resulting embryo ends up with nucleus DNA from its parents but mitochondrial DNA from a donor.

The DNA from the donor amounts to less than 1 percent of the resulting embryo's genes.

But Britain's decision to approve using the new methods will not open the floodgates to genetically modified babies. Clinics will need to apply to Britain's fertility regulator for permission to use the techniques on a case-by-case basis.

The decision was made after five years of reviewing the development, safety and efficacy of the procedures.