Eight young children are believed to be shielded from severe genetic disorders after being born through a procedure that replaces the mother’s faulty mitochondria with those from female donors.

Approximately 1 in 5,000 individuals inherit defective mitochondria, which are responsible for energy production in cells and passed down solely from mothers. Such defects can stem from genetic mutations leading to serious health issues like blindness, seizures, and even death. “Families face immense challenges with these conditions, as they are devastating,” said Bobby McFarland of Newcastle University in the UK.

In 2015, the UK became the first nation to sanction a technique known as pronuclear transfer for women at high risk of transmitting mitochondrial diseases who may not benefit from genetic testing prior to the transplant.

This technique involves utilizing eggs from both the mothers and donors, then fertilizing them with sperm from the father via IVF. After approximately 10 hours, the nuclei from both eggs are removed. This separates the crucial genetic material from the mitochondrial DNA.

The nucleus from the mother is subsequently inserted into the donor’s egg, resulting in an embryo that retains most of the genetic information from its biological parent while gaining mitochondria from the donor. It’s important to note that some maternal mitochondrial DNA could still be passed on unintentionally, as mentioned by Burt Smeet of Maastricht University in the Netherlands.

McFarland, who pioneered this approach with colleagues, has since employed the technique on 19 women possessing harmful mutations in over 80% of their mitochondria, typically the threshold for complications.

Following the transfer of the last embryo, seven women achieved pregnancies, resulting in the birth of eight healthy babies, including one set of twins.

Blood samples taken from the newborns were analyzed, revealing no harmful mitochondrial DNA mutations in five of them, while the other three showed only minimal levels. “The results have met our expectations,” noted Mike Murphy at Cambridge University.

Months or even years after undergoing nuclear transfer, some of the children have encountered challenges in reaching developmental milestones. Some have faced complications, potentially related to the transfer process. For instance, one child experienced elevated blood lipid levels and an irregular heartbeat, both of which were treated successfully, while another developed epilepsy at seven months, which resolved itself over time.

The research team intends to monitor the children to assess the long-term effects of this procedure.