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The preimplantation embryo and Jewish law

To the Editor:

We read with interest the report of Jon Evans in the News section of Nature Medicine1 summarizing the recent conference sponsored by the Progress Educational Trust entitled “Is the Embryo Sacrosanct? Multi-Faith Perspectives.” To our chagrin, the report provided a most misleading one-sentence summary of the normative Jewish Law (Halachic) perspective on this complicated major biomedical ethical issue.

The article states that under Jewish Law “an embryo is regarded as containing life in potential and should therefore be treated with the utmost care and attention.” In reality, this truism in no way reflects the detailed, practical, real-world implementation of the Halacha (Jewish religious law), a perspective that most definitely differs from the one that was promulgated in the recent Vatican proclamation entitled Dignitas Personae (The Dignity of a Person) or that was advocated by Lee Rayfield, the Anglican Bishop of Swindon.

Jewish law distinguishes six stages of human development, the first three of which are pertinent to the issue of stem cell research and our discussion: (i) the preimplantation embryo (from fertilization to implantation); (ii) the embryo (from implantation to identifiable organogenesis—that is, until 40 days after conception); (iii) the fetus (from organogenesis until potential viability—40 days after conception until 20 or more weeks); (iv) the viable fetus (from 20 or more weeks until onset of labor); (v) the 'dislodged' fetus (from the beginning of the second stage of labor until birth); and (vi) the neonate.

From this formulation, it is clear that the preimplantation embryo itself does not have the capacity to develop into a human being. If it is intended to be implanted, and if it is successfully done, only then does it acquire the full potential to become a human being. Thus, it is universally agreed by all Jewish law authorities that the preimplantation embryo does not have the same sacred title to life as the implanted embryo. Therefore, preimplanted embryos that are not designated for implantation, including their stem cell lines, can be used for potentially lifesaving and disease-curing purposes. In addition, the creation of in vitro preimplantation embryos for research is allowed, if it is probable that the research will ultimately help in saving human life.

Clearly, the implanted embryo cannot be used for research, and the arbitrary 14-day post-conception line of distinction is not recognized at all by Jewish law. However, the second stage, wherein the embryo is still not recognizable physically as a human and is to a degree comparable to 'mere water', allows a degree of flexibility for some rabbinic authorities, under specific circumstances, to permit an abortion.

A complete and detailed summary of this issue can be found in the report of the Bioethics Advisory Committee of the Israel Academy of Sciences and Humanities2, a report that served as the basis for the Israeli regulations that permit stem cell research.


  1. Evans, J. Nat. Med. 15, 4 (2009).

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  2. Israel Academy of Sciences and Humanities Bioethics Advisory Committee. Assia Jew. Med. Ethics 4, 39–54 (2004).

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Eidelman, A., Halperin, M. The preimplantation embryo and Jewish law. Nat Med 15, 238 (2009).

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