The study, which makes use of a technology called mitochondrial donation, has been described as a “tour de force” and “a remarkable accomplishment” by others in the field. In the team’s approach, patients’ eggs are fertilized with sperm, and the DNA-containing nuclei of those cells are transferred into donated fertilized eggs that have had their own nuclei removed. The new embryos contain the DNA of the intended parents along with a tiny fraction of mitochondrial DNA from the donor, floating in the embryos’ cytoplasm.
“The concept of [mitochondrial donation] has attracted much commentary and occasionally concern and anxiety,” Stuart Lavery, a consultant in reproductive medicine at University College Hospitals NHS Foundation Trust, said in a statement. “The Newcastle team have demonstrated that it can be used in a clinically effective and ethically acceptable way to prevent disease and suffering.”
Not everyone sees the trial as a resounding success. While five of the children were born “with no health problems,” one developed a fever and a urinary tract infection, and another had muscle jerks. A third was treated for an abnormal heart rhythm. Three of the babies were born with a low level of the very mitochondrial-DNA mutations the treatment was designed to prevent.
Heidi Mertes, a medical ethicist at Ghent University, says she is “moderately optimistic.” “I’m happy that it worked,” she says. “But at the same time, it’s concerning … it’s a call for caution and treading carefully.”
Pavlo Mazur, a former embryologist who has used a similar approach in the conception of 15 babies in Ukraine, believes that trials like this one should be paused until researchers figure out what’s going on. Others believe that researchers should study the technique in people who don’t have mitochondrial mutations, to lower the risk of passing any disease-causing mutations to children.
Long time coming
The news of the births has been long awaited by researchers in the field. Mitochondrial donation was first made legal in the UK in 2015. Two years later, the Human Fertility and Embryology Authority (HFEA), which regulates fertility treatment and research in the UK, granted a fertility clinic in Newcastle the sole license to perform the procedure. Newcastle Fertility Centre at Life launched a trial of mitochondrial donation in 2017 with the aim of treating 25 women a year.
That was eight years ago. Since then, the Newcastle team have been extremely tight-lipped about the trial. That’s despite the fact that other teams elsewhere have used mitochondrial donation to help people achieve pregnancy. A New York–based doctor used a type of mitochondrial donation to help a Jordanian couple conceive in Mexico in 2016. Mitochondrial donation has also been trialed by teams in Ukraine and Greece.