Revisiting the 14-day rule

August 31, 2020

Revisiting the 14-day rule

Megan Best

In many countries, embryos containing human cells can be grown in vitro for research purposes for up to 14 days. Established as a pragmatic compromise between ethics and scientific research, this rule is now coming under pressure as it stands in the way of technological advances.

Last year a Japanese scientist received government approval to develop animal-human hybrid embryos, in order to implant them into surrogate animals. The aim is to eventually produce animals, such as pigs, with organs made of human cells that can be transplanted into people. This has been made possible by the overturning of a ban forbidding the growth of embryos containing human cells beyond 14 days.

The 14-day limit for in vitro culture of human embryos was first proposed in 1979, in the early days of IVF, by the Ethics Advisory Board of the US Department of Health, Education, and Welfare. It was then endorsed in 1984 by the Warnock Committee—established to inquire into the technologies of in vitro fertilisation (IVF) and embryology—in the United Kingdom.

While acknowledging that embryonic humans should have a special status, the Warnock committee decided to avoid answering the question of when human life began. Instead it discussed how the embryo should be treated. Despite criticisms of this approach (how do you know how to treat it if you don’t know what it is?), the committee’s recommendation—that destructive human embryo research can be justified up to 14 days—has influenced policy makers around the world ever since.

The Warnock Committee chose their time limit on the grounds that 14 days was when the primitive streak was visible in the embryo (‘this marks the beginning of individual development’), and also the time when twinning was no longer possible. Of course, this science is now out of date. The human embryo is organised from its very first day and epigenetics can now demonstrate whether twinning is destined to occur way back at the beginning of embryogenesis. However, the Warnock report remains influential. At least 12 countries, including Australia, have encoded the 14 day rule in laws governing assisted reproduction and embryo research. The Warnock Committee’s thinking also permeates numerous government reports and scientific guidelines for embryo and assisted-reproduction research around the world.

Termination of the embryo at day 14 was a compromise between securing the benefits of research and assuaging society’s ethical concerns. The alternatives at each extreme—either banning embryo research altogether or imposing no restrictions on destructive research on human embryos— would have been unpopular public policy in a pluralistic society.

The 14 day rule was an artificial line in the sand which has been an effective policy tool, partly because it has been technologically difficult for scientists to break it. Until now. Recently, there have been reports of researchers sustaining human embryos in vitro for 12-13 days (previously cultures were rarely sustained beyond 7 days). Now that it appears feasible to grow human embryos beyond 14 days, many scientists are questioning the policy.

Human embryo research has always been divisive because of differing views on the moral status of the human embryo, and the fact that most research results in its destruction. Opinions differ on whether a human embryo has sufficient moral status that research on it should be prohibited. Educated debate no longer questions whether a human embryo is exactly that— human. However, it has been suggested that being human does not confer sufficient reason to protect the embryo.

Protagonists of destructive embryo research argue that protection is due only to human persons, and that personhood is not achieved merely on biological grounds. Arguments vary as to the moment in development at which personhood begins. Suggestions include: the point of fertilisation, when the egg and sperm are joined; implantation, when the one week old embryo has attached to the mother; quickening, or 40 days, as the time the soul enters the body; viability, when the child is mature enough to survive outside the womb; birth; or even after birth (which is an issue beyond the scope of this article).

Revisiting the 14-day rule might tempt people to try to rationalise or attack the philosophical coherence of the limit as an ethical tenet grounded in biological facts. It would be easy to do. Of course the rule doesn’t make sense philosophically. Either the pre-14 day embryo is being unjustifiably exploited (because the human embryo deserves protection), or research on embryos is being unjustifiably limited (because it doesn’t). But this misconstrues the restriction. The 14-day rule was never intended to be the line denoting the onset of moral status in human embryos. Rather, it is a public-policy tool designed to carve out a space for scientific inquiry and simultaneously show respect for diverse views on human-embryo research.

This was recognised at the time by an editorial in The Times which described the Warnock decision as ‘as convincing a statement of where sanity should rest as can be hoped for’ but also, more ominously stated that ‘It would be idle to pretend that such a limit is for all time, but for now the public would appear to accept it’.[1]

Destructive research on human embryos was first legalised in Australia with the Research Involving Human Embryos Act 2002, allowing researchers to use excess IVF embryos from IVF clinics. This legislative change occurred in response to proponents of embryonic stem cell research making remarkable claims regarding its promise for regenerative medicine (which are yet to be realised). But it turned out that IVF laboratories have traditionally used mouse embryos to test the quality of embryo culture media (which is used to grow the human embryos in the lab). With the legalisation of human embryo research, the question arose—should human embryos be used instead? After all, it was human embryos that they wanted to grow.

In fact, this is now occurring. Licenses have been approved for the use of human embryos in quality assurance exercises. Human embryos are also destroyed for the purposes of training laboratory technicians. The passing of an amendment to the 2002 law in 2006 which allowed the creation of human embryos for the express purpose of destructive research, meant that the supply will continue. This is a far cry from the proposed ground-breaking stem cell therapies for seriously ill patients which were the justification for this change in law.

The philosophical argument ultimately justifying the destruction of human embryos for research is the ethical theory of consequentialism. This is the argument that right and wrong can be determined by looking at the consequences of our actions alone. The end justifies the means. Our community has decided that, while the destruction of developing humans may be regrettable, the potential consequences of their destruction—such as a source of transplant organs through embryo research, or better chances of success in the IVF clinic—justify the act. Some proponents would go so far as to suggest that the potential benefits make it unethical not to pursue avenues such as medical research, and that those who raise ethical questions may lack compassion for those who are suffering debilitating disease.

But saying you might as well use unwanted embryos for research depends on the idea that there is nothing special about the human embryo. That it is not a human person, deserving of protection. It is, of course, an extension of the idea that the species homo sapiens deserves no special treatment, that we are not exceptional, that we are just an accident of an unguided evolutionary process, and not made in the image of God.

And that is why we can expect that the 14 day rule will continue to be overruled according to political expediency in the light of new breakthroughs in human embryo research. Yet, the embryo culture worked when we tested it with mouse embryos… are we sure there is nothing special about a human embryo?


Dr Megan Best is a medical doctor and bioethicist at the Institute of Ethics and Society at the University of Notre Dame Australia. She is the author of Fearfully and Wonderfully Made.



[1] Editorial, ‘A question of tolerance’, The Times, 24 April 1990.

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