Podcast Review: The ethics of growing human embryos in the lab

Should the current 14-day limit for growing human embryos in the lab be extended in light of recent breakthroughs? This was the question posed in the Guardian's Science Weekly podcast following news that embryos have been successfully developed for 13 days (see BioNews 850). An interesting and thought-provoking discussion concluded with a surprisingly cautious recommendation to engage public support before pressing for legal change. Ably moderated by their science editor Ian Sample, the expert panel comprised embryologist Dr Sue Avery; James Lawford Davies, a solicitor specialising in assisted reproduction; and bioethicist and philosopher, Professor John Harris.

Assuming no prior listener knowledge, the discussion reviewed and explained the law on growing embryos in vitro, the key biological milestones in their growth, and the ethical considerations – an ambitious feat in 36 minutes. The panel then examined the reasons behind the 14-day limit, and what benefits might be gained – or lost – by extending it.

John Harris supports extending the time period and views the 14-day limit as a very arbitrary answer to where to draw the line (1). It was justified by the appearance of the primitive streak, after which twinning can no longer take place and individuality is fixed. It is implied that the Warnock Report based this judgment on the concept of ensoulment (the point at which the soul might be thought to enter an individual body). Ensoulment was part of the dialogue at the time of the report's publication in 1984, as was recently noted in BioNews 850, but was not mentioned in the report itself.

The Warnock Report did discuss the view that embryo research is acceptable only if the embryo is incapable of feeling pain. Two alternative timings for the onset of sentience were considered: either the beginning of the central nervous system (around 22-23 days), or when its functional activity first occurs, which is thought to be several weeks later (2). A later cut-off time based on preceding sentience might have provided the issue of moral significance that John Harris considers lacking in the 14-day limit.

There was general agreement that Warnock's cut-off point has served its purpose in allaying public anxiety, demonstrating to the public that a line can be drawn and adhered to without creating a slippery slope. As two of the panel noted, there is great difficulty in justifying the timing through selecting a particular point in the embryo's continuous development. However, Baroness Warnock herself considers the 14-day rule to be the most important contribution her report makes, as she made clear in a recent interview with BioNews.

Provocatively, Ian Sample suggested that one reason the rule has lasted so well is because up until now, no one has been able to keep an embryo alive in vitro for as long as 14 days. It may also have been because the embryo only needed to grow to around five or six days to be used in current stem cell research, as was pointed out.

This raised the question of what benefits scientists might yield from an extra week's research. At this point, the panel became very wary. The feeling was that until there is a clear rationale for proposing a change in the time limit, reopening the debate might endanger current freedoms. John Lawford Davies pointed out that the Human Fertilisation and Embryology Acts also amended abortion laws, and while there are some inconsistencies between the two, reopening that debate is something no government will be keen to do.

Despite recommending a 21-day limit, John Harris believes this will only happen if a sufficient weight of civil society supports change. In order to gain such support, in my view, they need to be presented with clear moral reasoning for doing so, not just vague promises that we could learn much of scientific and therapeutic importance. Therapy delayed is therapy denied, he states – perhaps he is right, but as technological advances continue this could result in further calls for changes in the future, diluting public confidence that such limits will hold.

In my view, the limit ought to be extended on the basis of a moral argument – for example, that it is wrong to cause pain to a sentient creature. By selecting a conservative timing to ensure that the embryo cannot be sentient, the limit required might still prove longer than the 21-day limit suggested by John Harris. However, whereas technological advances may provide an argument for future changes to the time limit, with a link based on a moral rationale such as sentience this is unlikely.

This well-balanced and informative podcast didn't disappoint as an opening salvo in a debate aimed at engaging the public in reconsidering this controversial issue. It certainly made a refreshing change from the referendum debate.