Ethical Objections to Mitochondrial Replacement

Françoise Baylis  discusses the problems with creating children with three genetic parents.


Last week, the United Kingdom’s Chief Medical Officer, Dame Sally Davies, confirmed what many have long suspected. The UK is poised to go where no country has gone before – becoming the first country in the world to allow scientists to make human babies with genetic material from more than two people, using germ-line gene transfer.

In other countries, such as Canada, the development and use of mitochondrial replacement technology is illegal. The Assisted Human Reproduction Act prohibits altering “the genome of a cell of a human being or in vitro embryo such that the alteration is capable of being transmitted to descendants.”

Typically, babies are made from the sperm of one man and the egg of one woman.  But, some women’s eggs include unhealthy mitochondrial DNA (mtDNA). If these women reproduce using their own eggs, their children could be affected with a mitochondrial disease and this could result in serious health problems including neurodegenerative disease, stroke-like episodes, blindness, and muscular dystrophy. Scientists in the UK propose to avoid the vertical transmission of mtDNA mutations by replacing disease-linked mtDNA with healthy donor mtDNA to create children with three genetic parents: the man who contributes nuclear DNA; the woman who contributes nuclear DNA; and, the woman who contributes healthy mtDNA.

mtdnaThere are two experimental ways of doing this: both of which involve the transfer of nuclear DNA. One technique, called pronuclear transfer, involves transferring the pronuclei from a fertilized egg with disease-linked mtDNA into a fertilized egg with healthy mtDNA from which the nuclear DNA has been removed. The other technique, called maternal spindle transfer, involves transferring the spindle of chromosomes from an unfertilized egg with disease-linked mtDNA into an enucleated egg with healthy mtDNA. With either technique, the transmission of disease-linked mtDNA is avoided and the social parents are also genetic parents.

“Why should we care if children are born with nuclear DNA from one woman and mtDNA from another?  Moreover, why should we care if the female children born with non-familial mtDNA, in turn, pass this mtDNA on to their children?”

In defense of the plan to move forward with mitochondrial replacement technology, the UK’s Chief Medical Officer, says: “I think we will save some five to 10 babies born with ghastly diseases … and it will allow mothers to have their own babies, which at the moment they cannot.”

There are at least two problems with this claim.  There is the assumption that having children of one’s own requires having a genetic link to the children, and the suggestion that mitochondrial replacement is the only viable option. However, women at risk of having children with mitochondrial disease can have their own children using much less risky alternatives. For example, they can make a baby the old fashioned way, have prenatal diagnosis and, if the fetus is affected, they can choose to have a termination of pregnancy. Alternatively, they can make an embryo using IVF and have preimplantation genetic diagnosis followed by selective embryo transfer. They can have IVF and egg donation or embryo donation. They can choose to adopt a child. Using one or other of these options, women can become mothers without putting their future children in harm’s way with the use of mitochondrial replacement technology.

My point here is that while it is undeniably important to promote the birth of healthy children, research to develop mitochondrial replacement technology isn’t just about having healthy children, it is clearly also about satisfying the interests of prospective parents in having a genetic connection to the children they intend to parent. But why spend millions of tax payer’s dollars to fund research to meet the interests of a few women in having genetically related children?

The proponents of mitochondrial replacement technology are quick to downplay the potential for harm to offspring born following mtDNA replacement. They insist there is no evidence the technology is unsafe. The fact is we don’t know, and can’t know if the technology is safe (and effective) without investing considerable time, talent and money in research to investigate the potential short- and long-term harms to both the offspring and their progeny. The opportunity costs associated with this investment should give us all reason to question the path promoted by some in the UK, especially as there are safe and effective alternative ways for women at risk of having children with mitochondrial disease to become mothers.

In addition to concerns about the inappropriate reification of the gene and the potential harms to future children and their progeny, it is important to insist on the fact that the use of mitochondrial replacement technology marks a significant departure from the status quo. To date, there have been determined efforts to ensure that gene transfer research not even inadvertently involve heritable genetic modifications. With mitochondrial replacement technology, the non-familial donor mtDNA will be passed from the women to their children.  In turn, the female children will pass the non-familial donor mtDNA to their children, and so on down the female line. This is not inconsequential. Indeed, it has been suggested that this technology is a first step on the path to volitional evolution involving the pursuit of germ-line interventions for enhancement as well as therapeutic purposes.  This suggestion is not far-fetched, for surely this is not all about saving five to 10 babies at risk of mitochondrial disease.

For more on this topic, see: Baylis, F. (2013) The ethics of creating children with three genetic parents. Reproductive BioMedicine Online 26, 531-534.

Françoise Baylis is a Professor and Canada Research Chair in Bioethics and Philosophy, Dalhousie University, Halifax, Canada.

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