Bioethics @ TIU

“3-Parent Babies” Sally Forth

Posted December 1st, 2016 by Jon Holmlund

The journal Nature reports that scientists advising the U.K.’s Human Fertilization and Embryology Authority (HEFA) have judged that attempts to bring so-called “3-parent babies” to birth is “ready for limited clinical testing.”   Presumably this means that the underlying technology, mitochondrial replacement, has been tested enough in the laboratory that it’s ready to try for human procreation.  Also presumably, HEFA will promulgate rules or guidelines to address safety and other ethical issues.

I posted on mitochondrial replacement technology, or MRT, most recently this past February 25.  Follow the link for further background.  Other contributors to this blog have also written about it over the last couple of years.

As described in the report in Nature, the most salient worry seems to involve the effectiveness of the technology.  In a favored approach, a woman affected with a potentially serious genetic disease involving genes in her mitochondria has the nucleus of one of her eggs, which has most of her genes which in turn are normal, transferred into a fully healthy egg from another woman donor.  The resulting egg is then fertilized in the lab (i.e., fairly standard IVF), and would then be implanted into the mom for pregnancy, and so on it goes.   The worry?  That some of the abnormal mitochondria come along for the ride, so that the transfer is not “pure,” as it were.  In that case, the disease could still be handed down to the offspring if enough abnormal mitochondria stowed away.

This has been tested in the lab by doing the egg nuclear transfer and fertilization, creating human embryos (i.e., tiny new human beings) and then growing up cells from them to see what happens, and indeed the abnormal mitochondria persist at least some of the time.  This research necessarily involves the destruction of the human embryos.

No embryos have been implanted into a woman’s womb in the Anglosphere, to my knowledge, bur there have been recent reports that at least one baby boy has been born, in Mexico, after a fertility doctor from New York City performed the technique there, and that the baby looks healthy but has abnormal mitochondria in at least some of his tissues.  It’s not at all clear how many abnormal mitochondria are needed to transmit the disease, or whether genetic matching of the woman donating the healthy egg and the disease-affected prospective mom can reduce the risk of the offspring inheriting the disease.

But the U.K. wants to do this clinical work there, in hopes that people won’t go to places like Mexico or Ukraine to get the procedure.

As I’ve written before, mitochondrial diseases are quite rare, and one might favor pursuing this reproductive technology as a special case, but apart from the concern about destruction of human embryos in the course of developing the technology, one must also be concerned that it will be quickly applied more broadly, in the attempt to treat infertility in general or as a misguided shot at human enhancement.

Personally, I would have never “gone there” in the first place.  But this horse has long-since left the barn, so a desire to collect data, proceed cautiously, and try to control applications looks wise, as far as it goes.  Besides the UK, the U.S. is a potential site of regulated work in MRT, depending, as I noted in February, on whether the government allows it to be funded and whether the several concerns raised by the Institute of Medicine, at a minimum.

Will any boundaries on MRT hold, in the end?  I’m skeptical.  But a strict limitation to the rare cases of genetic mitochondrial disease should at least be held inviolate.

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