In 2015, the United Kingdom became the first country to legalize a procedure called Mitochondrial Replacement Therapy (MRT), which was used to prevent inheritable health conditions involving the heart, brain, and muscles caused by mitochondrial mutations. This MRT procedure, sometimes called three-person in vitro fertilization (IVF), involves transferring genetic material from the nucleus of the egg or embryo with mitochondrial mutations to a different healthy donor egg with its genetic materials previously removed, allowing the child produced to have three parents.

Early human embryos

Eight years later, the Human Fertilization and Embryology Authority (HFEA) of the United Kingdom confirmed that at least one UK child had been born using the procedure as of April 2023. Although this is the first successful case of a fully legalized MRT procedure, it has previously been done successfully unregulated as well. A US doctor used MRT successfully to prevent mitochondrial disease in a baby in Mexico in 2016. Another US doctor, John Zhang, and his team successfully performed IVF on an embryo at New Hope Fertility Center in New York City in 2016. Greece and Ukraine have also conducted MRT to treat infertility. Despite many successes and new countries such as Australia approving MRT in 2022, MRT remains restricted in most areas, including the United States. The extent of IVF’s effectiveness is still to be tested. When, inevitably, a small number of mitochondria are transferred into the donor egg or embryo, it’s unclear whether or not very low levels of mutation-bearing mitochondria cause health problems. Additionally, scientists estimate a 1 in 50 chance of a mismatch in mitochondrial DNA and nuclear DNA could result in mitochondria problems. In some cases, a phenomenon known as reversal, where the carried-over mitochondria can increase markedly over time, replacing donor mitochondria in cells and bringing back the mutation. From scientist Wells’ observation in Greece, of the 6 children born with MRT, 1 child experienced reversal, though the reversal seems to have had no effect on the child’s health. The reason for this phenomenon is not clear, but scientists hypothesize that, due to efficiency reasons, matching donor and recipient on their mitochondrial DNA or freezing the mother’s eggs before transferring the nuclear genetic material into fresh donor eggs could prevent reversal. The process of Mitochondrial Replacement Therapy (MRT) is related to our understanding of mitochondria. From what we’ve learned, mitochondria are passed down only by females and mothers, as a significant amount of mitochondrial DNA exists inside eggs from mothers, whereas no mitochondrial DNA exists in the sperm of males, and all mitochondria are lost during fertilization. This leaves the mitochondrial DNA of the embryo and child originating solely from the mother’s egg. This explains why it is not possible to be treated with simple medicine, as the mutations are passed down genetically, requiring this procedure. Although I think the other side of natural selection should be considered by scientists before widely spreading the use of this procedure, the fact that MRT is life-saving and allows families to be formed outweighs the natural philosophies, and it should be widely used one day. If you needed MRT to give birth to a healthy child, would you do it?

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