Eight Babies Born Free of Mitochondrial Disorders Using Three-Parent IVF in UK

The method, known as pronuclear transfer, involves replacing the mother’s faulty mitochondria with healthy mitochondria from a donor. Mitochondrial diseases can affect organs that need a lot of energy, such as the brain, heart, liver, muscles, and kidneys, and are caused by mutations in mitochondrial DNA.

One child is now two years old, two are between the ages of one and two, and five are infants. All were born healthy, and tests showed either no or low levels of mitochondrial mutations. According to the researchers, the children have had normal development so far.

"This process essentially replaces the faulty mitochondrial DNA (mtDNA) with healthy mtDNA from the donor," said Professor Mary Herbert, a senior researcher and professor of reproductive biology at Newcastle University, during a press briefing.

The procedure was carried out in 22 women whose children were likely to inherit mitochondrial conditions. Eight of them gave birth, and one more is currently pregnant. Seven pregnancies were without issues, while one involved high lipid levels. There were no miscarriages.

The process starts by fertilizing the mother's egg with the father's sperm. The pronuclei, which carry genetic material from both parents, are removed and transferred into a donor egg that has had its own pronuclei removed. The resulting embryo has nuclear DNA from the parents and mitochondrial DNA from the donor.

According to the report, six of the newborns had 95% to 100% lower levels of mitochondrial mutations compared to their mothers, while two had 77% to 88% lower levels.

"These data indicate that pronuclear transfer was effective in reducing transmission of mtDNA disease," the researchers stated.

Dr Andy Greenfield, a reproductive medicine specialist at the University of Oxford who was not part of the research team, commented, "These results are the culmination of decades of work—not just on the scientific and technical challenges but also in ethical inquiry, public and patient engagement, law-making, drafting and execution of regulations, and establishing a system for monitoring and caring for the mothers and infants."

He added that the data is likely to support future studies, "The researchers’ 'treasure trove of data' is likely to be the starting point of new avenues of investigation."

The scientists also tested another method where the mother’s unfertilized egg nucleus is moved into a donor egg and fertilized afterward. They said the pronuclear transfer method may provide a more reliable way to prevent disease transmission.

The UK approved research into mitochondrial donation in 2015, becoming the first country to do so. In contrast, the United States banned the procedure for human use the same year through a congressional measure that prevents the FDA from reviewing cases involving heritable genetic modification.