A government-convened panel of scientists and bioethicists have decided that it is ethically permissible to go forward with an in-vitro fertilization technique that uses genetic material from two mothers and one father to create an embryo, “so long as significant conditions and restrictions are in place.”
The procedure is known as mitochondrial replacement therapy. To do it, doctors take a donor egg containing healthy mitochondria and remove its nucleus. They then replace it with the nucleus from one of the mother’s eggs and use sperm from the father’s egg to fertilize it. The resulting embryo gets the majority of its genetic information from its parents and a tiny amount, 0.1 percent, from the donor egg. (Mitochondrial DNA contains 37 genes and is only found in eggs; nuclear DNA contains an estimated 30,000 to 40,000 genes.)
There are number of serious diseases that mothers can pass along to their children by way of the mitochondria, which are the intracellular organs that serve as the “digestive system” of the cell. Currently, mothers with mutated mitochondrial DNA are advised to use donor eggs if they want to have children. Because mitochondrial sperm is only found in eggs, and not sperm—and as such only mothers can pass down the associated diseases—scientists recommend limiting the procedure to making only boy babies for the meantime. This way, if there are any unforeseen side effects in a three-parent baby’s mitochondrial DNA, it will not be passed down to future generations.
The recent decision is the result of a panel convened by the Institute of Medicine, at the request of the Food and Drug Administration. The FDA says it will review the report, but won’t be able to approve any clinical applications because of a recent Congressional ban. As the Washington Post reported, the omnibus fiscal budget bill for 2016 prohibits any procedure “in which a human embryo is intentionally created or modified to include a heritable genetic modification.”
According to an NPR story on the procedure, some critics fear that it could introduce unforeseen errors into the human gene pool that might lead to new diseases. Others worry that it is a slippery slope from replacing mitochondrial DNA to the creation of designer babies, offspring that has been genetically modified for beauty, intelligence or to be disease-free.
These issues came up in the debate over three-person babies that took place in the United Kingdom last year, where the procedure was ultimately okayed on the basis that the potential benefits outweighed the risks. At the House of Lords, Lord Robert Winston, fertility doctor and in-vitro-fertilization pioneer, said, “I don’t believe, my Lords, in spite of what we’ve heard this evening, that this technology threatens the fabric of society in the slightest bit.” The majority agreed.