The decision by the British government earlier this summer to approve a suite of new technologies that would make possible the creation of human embryos with three genetic parents has brought a long-simmering and seemingly obscure bioethical debate into the public eye, raising questions not only about the future of human reproductive technologies but also about some practices that have been with us for decades.
The British decision followed recommendations from the country’s Human Fertilisation and Embryology Authority in March of this year and a major bioethics report cautiously endorsing the techniques last year. The debate has muddied the lines between left and right. Liberal groups like the Center for Genetics and Society strongly oppose the new technologies, while some liberal bioethicists like Arthur Caplan have said the new techniques are “worth the ethical risk.” Conservative bioethics commentator Wesley J. Smith, a frequent contributor to these pages, has argued that the new technologies are unethical, while the editors of Real Clear Science, who are scourges of the “antiscientific left,” have endorsed the new technologies.
The techniques in question involve transplanting the chromosomes from a single-cell embryo or from an unfertilized egg into a donor egg or embryo from which the chromosomes have been removed. These procedures were developed with a therapeutic intention: They would allow women with mitochondrial disorders to have children who will not inherit those disorders. (Mutations in the mitochondrial DNA can cause a host of serious illnesses.) Unlike in egg or embryo donation, which are methods widely used at in vitro fertilization clinics and would prevent the transmission of these disorders, the children created through the new techniques would be genetically related to the women undergoing the procedure, having inherited her nuclear DNA but not her mitochondrial DNA. What has been most controversial about these techniques is that they would create embryos with three genetic parents: The embryos would inherit chromosomes from one mother and one father, but would also inherit mitochondrial DNA (which contains a small number of additional genes) from the donated embryo or egg cell.
Before focusing on the three-parent issue, let us first look at other objections that have been raised. As Alex Berezow of Real Clear Science notes, some critics “worry about the ethics of destroying embryos,” since one of the new techniques involves the destruction of embryos. But he dismisses this concern by pointing out that “standard IVF also destroys embryos,” which is, unfortunately, all too often true, though this new way of making babies would destroy embryos in a different way from the usual practice of IVF.
The new embryo-destructive technique, known as “pronuclear transfer,” involves an early-stage embryo—one in which the chromosomes from the egg and sperm have not yet joined together in a single nucleus. The pronuclei are extracted, destroying that embryo. The extracted genetic material is then transferred into another, similarly enucleated (and thus destroyed) embryo, but one that was created using a donated egg, thereby creating a new embryo that contains the chromosomes of the man and woman who intend to become parents, as well as the mitochondrial DNA of the egg donor. The destruction of embryos in ordinary IVF results from the discarding of “excess” embryos, or of embryos deemed genetically defective following screening tests. This new technique would be the first assisted-reproductive technology involving the deliberate destruction of human embryos as a necessary part of the procedure.
Berezow is of course correct that countless human embryos are destroyed on a regular basis as a result of the way IVF is practiced in the United States today. That might also lead us to ask whether we have been right to tolerate the cavalier destruction of embryos as just part of the way the U.S. IVF industry does business. Indeed, ordinary IVF could be practiced in a way that would not result in the destruction of human embryos; in Germany, for instance, it is illegal to create “excess” embryos during IVF treatments.
Another objection to these new techniques relates to the risks they will pose to the created children. While there have been a few preliminary studies, the risks are still poorly understood. Against these critics, Berezow writes that “a mother with a mito-chondrial disease who wishes to have her own children may very well choose to accept the risk.” Indeed she may, but the child born through this experimental procedure is obviously in no position to accept the risk.