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Embryo experimentation: is there a case for moving beyond the ‘14-day rule’

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Abstract

Recent scientific advances have indicated that it may be technically feasible to sustain human embryos in vitro beyond 14 days. Research beyond this stage is currently restricted by a guideline known as the 14-day rule. Since the advances in embryo culturing there have been calls to extend the current limit. Much of the current debate concerning an extension has regarded the 14-day rule as a political compromise and has, therefore, focused on policy concerns rather than assessing the philosophical foundations of the limit. While there are relevant political considerations, I maintain that the success of extension arguments will ultimately depend on the strength of the justifications supporting the current 14-day limit. I argue that the strongest and most prevalent justifications for the 14-day rule—an appeal to individuation and neural development—do not provide adequate support for the limit of 14 days. I instead suggest that an alternative justification based on sentience would constitute a more defensible basis for embryo protection and that a consideration of such grounds appears to support an amendment to the current limit, rather than the retention of it. While these conclusions do not establish conclusively that the current limit should be extended; they do suggest that an extension may be warranted and permissible. As such, this paper offers grounds on which a reassessment of the 14-day rule may be justified.

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Notes

  1. As to what specific standards are relevant will depend on the type of restriction being revised (e.g. legislation, institutional guidelines, professional standards). However, a common theme that has emerged in the debate is that any revision ought to involve a slow, deliberative and inclusive dialogue between the public, experts, and policy makers (Hyun 2016; Warnock 2017; Sample 2016; Appleby and Bredenoord 2018; Cavaliere 2017).

  2. See for example Devolder and Savulescu’s (2006) views on the moral imperative to conduct beneficial research.

  3. The earliest mention of a 14-day limit on embryo research is found in a 1979 U.S. report. Although, due to various political reasons the recommendation was never given the opportunity to be properly reviewed (Ethics Advisory Board, Department of Health, Education, and Welfare 1979; Hyun 2016).

  4. The primitive streak is a thickened linear band on the epiblast that is formed by cell growth and migration. This signals the beginning of gastrulation, a process in which the body plan of the embryo is formed (Moore et al. 2015).

  5. For a discussion on the relevance of implantation see: Fischbach and Fischbach (2004), Harris (2007), Pera (2017), or Singer and Dawson (1990).

  6. In the introduction to a 1985 publication of the Warnock Report, Mary Warnock has offered a contradicting position, stating that: “The majority of the Committee was not moved by the argument that these cells could, if certain conditions were satisfied, become human beings. They did not rely, that is to say, as the minority did, on “potentiality”, but on consideration of what the embryo was at a particular time immediately after fertilisation.” (Warnock 1985, p. xv). Michael Lockwood has proposed two possible ways in which the apparent contradiction may be resolved. The first is that the mention of the potential of the embryo to become a human being in the Warnock Report is an acknowledgment and dismissal of the common argument for protection. The second is that in the 1985 introduction, Mary Warnock is suggesting that the majority of the committee only rejected the significance of potentiality immediately after fertilisation, and not at some later point. Lockwood does not consider either to be plausible and suggests that the mention of potential may be somewhat unintended (Lockwood 1988, p. 211).

  7. Such reasons included practical and theoretical challenges associated with settling moral questions, and also philosophical views of Mary Warnock. Specifically, her opinions regarding moral sentimentalism, intuitionalism and moral authority, see for example (Wilson 2014, pp. 140–186).

  8. There are other non-individuation arguments that appeal to the lack of distinction between embryoblast and trophoblast, and to the totipotency of blastomeres. However, these arguments face similar problems. See for example: Oderberg (2008).

  9. Although there has been no conclusive evidence regarding the exact timing and process that results in conjoined twins—largely because of the inability to observe the embryo during the ‘black box’ period—according to the most widely held theory (fissure theory) conjoined twins are believed to form between day 13 to 17 of gestation (see for example: Hall 2003; Weber and Sebire 2010; McNamara et al. 2016). Until it is possible to observe embryo development beyond 14-days, the precise point at which twinning (of any kind) is no longer possible may indeed be contested.

  10. Although it is not made clear in the Warnock Report, I take it that “functional activity” refers to the development of active neural circuits. This would require, at a minimum, the differentiation of electrophysiologically active neurons and synapse formation. See: Johnson et al. (2007) and Zhang and Poo (2001).

  11. Because it is specifically acknowledged in the Warnock Report as the grounds for the protection of the embryo.

  12. For example: a prince is a potential king yet does not have the rights of a king until he becomes an actual king (Stier and Schoene-Seifert 2013, p. 20).

  13. See for example: French et al. (2008)

  14. While I do not necessarily endorse the reductio objection, the possibility for germ cells and somatic cells to develop into a human being (and possibly a human person) presents a problem for potentiality arguments for the protection of the embryo. To avoid such a problem, it has been argued that there is a morally relevant difference in potential between a human embryo and human somatic cells or germ cells (e.g. by making a distinction between proximate and remote, or active and passive potential) (Condic and Condic 2018). However, these proposals still face a number of challenges. See for example: Stier and Schoene-Seifert (2013).

  15. I use the term ‘procreative embryo’ to refer to in vitro and in vivo embryos that are part of a procreative project. Namely, those that are intended for gestation and eventual birth.

  16. Sentience as a criterion of moral considerability is generally defined as the capacity to feel pleasure or pain (Kuhse and Singer 1990; Warren 1997). However, there is some ambiguity concerning the concept, particularly regarding the aspect of ‘feeling’. Interpretations of sentience range from the rudimentary capacity to respond to external stimuli, to self-conscious awareness (van Bogaert 2004; Bortolotti and Harris 2005). My use of ‘sentience’ will refer to ‘pain sensation’, a capacity that sits somewhere between these two extremes. Specifically, I am referring to a capacity for the (conscious) sensation of pain that is more complex than a simple reflex response yet does not involve any higher-level self-conscious pain awareness. I suggest that this form of ‘minimal’ sentience should be considered as sufficient and not necessary to prohibit research. That is, there may be other sufficient criteria that would prohibit research even in the absence of pain sensation (e.g. future interests of the embryo). Furthermore, I am suggesting that this conception of sentience may serve only as a criterion for moral considerability and not full moral status.

  17. A limit based on sentience could also be formulated as a temporal limit, thereby satisfying what many consider to be a particularly useful characteristic of the 14-day rule. Namely, that it relies on an easily tracked period of time (i.e. number of days) (Chan 2018).

  18. This is my own term, used to designate the types of properties or features relevant for my proposed criterion. A version of this proposal has also been presented as a possible strategy to address the difficulties current regulations face when dealing with Synthetic Human Entities with Embryo-like Features (SHEEFs) (see: Aach et al. 2017).

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Acknowledgements

I would like to thank Dr. Mianna Lotz for her supportive and helpful discussions and feedback on previous drafts.

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    Grant Castelyn

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Castelyn, G. Embryo experimentation: is there a case for moving beyond the ‘14-day rule’. Monash Bioeth. Rev. 38, 181–196 (2020). https://doi.org/10.1007/s40592-020-00117-x

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