Stop fretting about 3-parent embryos and get ready for "multiplex parenting"

The controversy over three-parent embryos could soon be old hat. Writing in one of the world's leading journals, one of Britain's best-known bioethicists has outlined a strategy for creating children with four or more genetic parents. He calls it "multiplex parenting".

John Harris, of the University of Manchester, and two colleagues, César Palacios-González and Giuseppe Testa contend in the Journal of Medical Ethics (free online) that this is one of many exciting consequences of using stem cells to create synthetic eggs and sperm. (Or as they prefer to call them, in vitro generated gametes (IVG).)

After the discovery of induced pluripotent stem cells in 2007, theoretically any cell in the body can be created from something as simple as a skin cell. Mice have already been born from sperm and eggs created from stem cells. Harris and his colleagues believe that the day is not far off when scientists will be able to do the same with humans. In their paper, they spin an ethical justification for this and outline some possible uses.

First, is it ethical? Of course it is, so long as experiments on mice show that it is safe. After all, they write, this is already a much higher ethical bar than the one used for the first IVF babies. "If impractically high precautionary thresholds were decisive we would not have vaccines, nor IVF, nor any other advance. Nothing is entirely safe." Besides, any children brought into the world are better off than if they never existed.

Second, there are many potential uses. The first four are familiar from the world of IVF: men who cannot produce viable sperm; women with premature menopause; people who have lost gonads or their fertility due to cancer treatment; and people who have been involuntarily sterilised (rare, but they do exist).

Many clients for such a service would be gay and lesbian couples who could have children who are genetically related to them both. "There is nothing morally wrong with same-sex competent caring people using IVG for satisfying their legitimate interests in becoming genetic parents of their children," they say.

Another would be "single individuals, who may wish to reproduce without partner and without resorting to gamete donation". This would be the most intense form of incest – an individual effectively mating with himself – so its safety is not guaranteed. But if it were safe, it might be permissible.

Finally, "multiplex parenting", an option which Harris and his colleagues tackle with great enthusiasm. This is "a radical expansion of reproductive autonomy that allowed more than two persons to engage simultaneously in genetic parenting".

"IVG could permit instead a much more substantive sharing of genetic kinship, through what is in essence a generational shortcut. Imagine that four people in a relationship want to parent a child while being all genetically related to her. IVG would enable the following scenario: first, two embryos would be generated from either couple through IVF with either naturally or in vitro generated gametes. hESC lines would be then established from both embryos and differentiated into IVG to be used in a second round of IVF. The resulting embryo would be genetically related to all four prospective parents, who would technically be the child's genetic grandparents."

But it could be far more than four parents. An Australian bioethicist has discussed how children with even more progenitors could be created as a form of in vitro eugenics. By creating gametes from embryonic stem cells, it would be possible to create 20 or 30 generations of Petri dish humans in as little as ten years. So four parents might be a conservative estimate. "The in vitro compression of generational time appears thus like the most transforming feature of IVG derivation," they write.

An ethical defence of this scenario is tall order. But Harris et al are up to it. In the first place, arguments drawn from what is "natural" are obviously irrelevant as there is no such thing as "natural" ways of acting. Hence, what can be wrong with opening up genetic kinship to a wider range of people than one father and one mother?

If there are some drawbacks, the child can hardly complain. It exists, and existence is better than non-existence. In any case, even today, parenting involves many different individuals from different generations. The use of IVGs merely gives this reality a genetic component. "Prospective parents will be able to choose among a hitherto unimaginable variety of potential children," they write. 

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