Three-parent babies are already approved in the U.K., and they should be in the U.S. too, according to a new report by the National Academies of Sciences, Engineering, and Medicine. But that doesn’t mean pushing the “go” button and immediately allowing the procedure to go ahead; to address concerns and safety issues, certain restrictions should be put in place that guide further clinical investigations, the document advises. If these ultimately show that the assisted reproduction technique is safe, then at a later date the limitations may be lifted.
The report, requested by the U.S. Food and Drug Administration (FDA), concerns a controversial procedure known as mitochondrial replacement (MRT). Mitochondria are little sausage-shaped structures inside the cell that generate energy. They also contain their own small genome, known as mitochondrial DNA (mtDNA), which is, unfortunately, prone to mutations. These potentially dangerous events occur at a rate around 10 times faster than in our main genome, housed in the nucleus.
If these mutations prevent the mitochondria from functioning properly, serious problems can ensue in the affected individual. The resulting diseases are incurable, severely debilitating and often fatal. But there is a way to prevent children from inheriting them, and it technically involves three parents.
Mitochondria are considered the "powerhouses" of cells, and contain fewer than 40 genes. Designua/Shutterstock
For the procedure, faulty mitochondria are replaced by those from the egg of a healthy, disease-free donor, either before or after the egg is fertilized in a test tube. Sperm contains hardly any mitochondria, which is why the technique involves only donor eggs and explains why the disease is only inherited from mothers. That is also the reason why the new report recommends that initial clinical investigations only involve male embryos.
“Because mtDNA is solely inherited from the mother, MRT producing female offspring would constitute heritable genetic modification, also known as germline modification, as these children could pass on these genetic changes,” the report explains. But with time and more data, both from long-term human and animal studies, hopefully the restriction will be loosened to allow both females and males to be born from the procedure.
The report also touches on the potential psychological impacts that may result from a child having three parents, including identity issues and confusion over ancestry. While these ethical complexities need to be considered, the authors suggest that they shouldn’t represent an obstacle to approval, but rather something that should be discussed by all parties involved to ensure the welfare of the child.
At the moment, it’s unclear as to whether the green light will ultimately be given by the FDA – they are still in the process of reviewing the report. But as the technique has been defined as a form of genetic modification, and modified embryos aren’t currently allowed to be implanted into women in the U.S., getting approval may be a timely and complicated procedure.