Three-parent baby technique could create babies at risk for serious illness

We know of one case where it doesn’t seem to have worked. A baby is born from an embryo that PGT has shown contains about 12% of the mother’s “bad” mtDNA. But by the time the baby was born, the proportion had jumped to around 50%. This baby had a plethora of symptoms, including atypical brain development, behavioral issues, and signs that he had suffered a brain hemorrhage.

Only a small number of babies are born after using PGT to screen for mitochondrial disease, so again it’s hard to draw conclusions. The French center that pioneered the treatment and has been offering it since 2006 recently reported that it had only 29 babies born this way, Heindryckx says. Her own center has only used it for births of four or five babies in the past 10 years. And, as with MRT reversal, there’s a chance that babies who aren’t sick at birth will get sick as they get older.

“It’s alarming,” says Heindryckx. “We should also follow babies born after PGT, because it could be that this reversion is happening there as well.”

A dangerous alternative?

What does this mean for MRT in the meantime? While the Newcastle team plans to continue their trial, others warn that, for now at least, we should put the use of MRT for mitochondrial disease on hold and instead study it in people who don’t have not such diseases, as those with infertility.

Mazur himself refuses to use MRI for mitochondrial diseases. And Heindryckx says the risk is too high for him – with a 20% risk of reversion, he says, there’s no way his institution’s ethics committee would allow him to use MRT for a mitochondrial disease.

Mertes says she was never a fan of MRT trials. Scientists knew in advance that the trials were never going to be risk-free and involved a potential waste of eggs and embryos from perfectly good donors. “Ultimately, you’re presenting patients with an option that’s more dangerous than their alternative,” she says.

Experimental treatments like MRT also help reinforce the idea that it’s very important for parents to have a genetic connection to their children, Mertes says. “Wouldn’t it be wiser to ask if it’s so important to have that genetic connection if the price you have to pay is a risk to your child’s health?” she asks. Parents can avoid all the risks associated with MRT by choosing to use a donated egg instead of their own or by adopting a child, for example.

In the meantime, clinics that offer MRT need to update the information they provide “so people know this is a very real risk they’re taking,” Mertes says. And she and Prior believe treatment should be limited to those who “need it” or at least are adamant they want a genetic link to their children.

Mitalipov is confident that scientists like him will eventually find a solution to mitochondrial reversion. “We just have to figure out why it’s happening,” he says. “So far no idea… but just give us time.”