Every few months, a story pops up about a new frontier in reproductive medical technologies: so-called “three-parent IVF.” NPR recently reported on efforts in Britain to allow embryos created via this technique to be transferred into women’s uteruses, while a New York Times Magazine cover article last summer focused on whether the Federal Drug Administration would approve human clinical trials.
The three-parent IVF technique engenders controversy partly because all reproductive technologies do, but also because it would be the first technique to make germ line-level changes in human embryos – changes to an embryo’s DNA that could be passed on to future generations. The technique manipulates mitochondrial DNA (mtDNA). Our mitochondria convert oxygen into energy and power our cells; mtDNA exists separately from our other DNA, and is passed straight from mother to child without recombining with the father’s DNA. In the “three-parent” IVF technique, mtDNA from one woman’s egg is removed and replaced with mtDNA from another woman’s egg, and the egg is then fertilized. A child born as a result would still inherit half of his/her regular DNA from the father and half from the mother. But his/her cells would also contain donor mtDNA. Researchers hope the technique would allow women with a family history of mitochondrial disorders (which can range from mild to fatal) have healthy children.
By producing heritable genetic changes in human embryos – changes which essentially result in three-parent babies – this technique would cross an ethical bright line that many researchers and ethicists agree ought not to be crossed.