LONDON — Eight Babies Born with Experimental Technique

Researchers announced Wednesday that eight healthy babies were born in Britain using an experimental method that incorporates DNA from three individuals. This technique aims to help mothers evade passing on serious rare diseases to their offspring.

Typically, DNA is found in the cell nucleus—this inherited material defines our traits. However, there’s also some DNA found outside the nucleus, located in mitochondria. Mutations in these structures can lead to various diseases in children, resulting in symptoms that range from muscle weakness to organ failure and even death.

Standard testing during in vitro fertilization usually detects these mutations, but sometimes it’s unclear.

Scientists have been refining a technique to sidestep these issues by utilizing healthy mitochondria from donor eggs. They reported in 2023 that the first babies born through this approach involve transferring genetic material from the mother’s egg into a donor egg that contains healthy mitochondria but has its own key DNA removed.

Dr. Zev Williams, director of the Columbia University Fertility Center and not involved in this research, mentioned that the latest findings “mark an important milestone.” He believes this expanded range of reproductive options will empower more couples to seek safe and healthy pregnancies.

This method results in embryos carrying DNA from three sources—the mother’s egg, the father’s sperm, and the donor’s mitochondria. A change in U.K. law in 2016 made this possible, and while it is also legal in Australia, many other countries, including the U.S., still prohibit it.

Experts from Newcastle University in Britain and Monash University in Australia shared findings in the New England Journal of Medicine Wednesday. They reported conducting this new technique on fertilized embryos from 22 patients, resulting in eight babies believed to be free from mitochondrial diseases. One woman remains pregnant.

Interestingly, one of the eight babies had slightly elevated levels of abnormal mitochondria, which, according to Robin Lovell-Badge, a genetic scientist at the Francis Crick Institute who wasn’t part of the study, isn’t currently high enough to be worrisome but should be observed as the child grows.

Andy Greenfield, a reproductive health specialist at the University of Oxford, described this development as “highly significant.” He noted that this mitochondrial exchange method would only be applicable to a limited number of women who can’t use other strategies to avoid passing on genetic disorders.

The technique was legalized a decade ago, so many have been anticipating this report. “Fortunately, the children seem healthy,” he remarked in an email.

Ongoing monitoring of these children may be crucial for confirming their continued health, he added.

Lovell-Badge pointed out that the donor’s contribution is tiny, explaining that the genetic material from the donor makes up less than 1% of the child’s composition. He compared it to bone marrow transplants, stressing that they tend to involve far more DNA from another individual.

In the U.K., couples wishing to conceive via donated mitochondria must receive approval from the nation’s fertility regulator.

Some critics have expressed concerns about the potential long-term impacts of such innovative techniques on future generations. “Currently, pronuclear transfer is not permitted for clinical use in the U.S. due to regulations against heritable genetic changes,” stated Williams. Whether this will change remains uncertain and will likely hinge on the evolution of scientific, ethical, and policy discussions.

For almost ten years, U.S. Congress has included clauses in annual funding bills that prevent the FDA from accepting applications for clinical studies involving modifications to create heritable changes in human embryos.

But in nations where the technique is legal, advocates suggest it could offer a promising alternative for families in need.

Liz Curtis, whose daughter Lily passed away from a mitochondrial disease in 2006, now collaborates with other families facing similar challenges. She shared her own devastating experience of being told there was no treatment for her baby and that death was inevitable. The diagnosis “turned our world upside down,” she recalled, adding that it was frustrating not to have clear information about the condition.

Curtis eventually started the Lily Foundation to promote awareness and research regarding mitochondrial diseases, including the work being conducted at Newcastle University. “This is incredibly exciting for families desperate for hope,” she said.

The U.K.’s Human Fertilisation and Embryology Authority welcomed these findings, clarifying that this technique will only be available to those very high risk of passing on these conditions. As of now, 35 patients have received the go-ahead to undergo this procedure.