Preimplantation embryo

Preimplantation in human embryonic development

The word pre-embryo is sometimes used in ethical contexts to refer to a human embryo at least between fertilization and implantation, though this term has not been adopted by the scientific community. The stage is more recognised as the preimplantation embryo.

Implantation begins about six days after fertilization, and lasts for about a week, during which time formation of the primitive streak occurs.

Use of the term pre-embryo, in the context of human development, has drawn criticism from opponents of embryo research. From scientists who have considered this categorization invalid or unnecessary. One rationale that has been advanced for distinguishing an early fertilized human conceptus from an embryo is that there is a potential for the conceptus to split into identical twins prior to implantation, and so (the argument goes) the conceptus cannot be regarded before implantation as a single human being. However, the conceptus before implantation exhibits self-actuated activity, which has led to the assertion that it is an embryo.

Ontological status

• (o) indicates the (natural &) standard reproductive and embryogenic pathway
• (mz) indicates all the possible pathways for a monozygotic twin (see Scott, 2002, Hall, 2003, for a review on monozygotic twinning)
• (/c) indicates a clone created by either SCNT or ANT (See Hurlbut, 2005, and section III. Pluripotent Stem Cells Derived from Biological Artifacts in the PCBE's Report on alternative sources of stem cells for a review of ANT))
• (ch) indicates all the possible pathways for a chimeric individual (see Charles E. Boklage, 2006, for a review on chimerism and twinning)
• (dz) indicates the pathway of a dizygotic twin
• (en) indicates an enucleated oocyte
• (m) indicates a hydatidiform mole
• (cm) indicates a complete hydatidiform mole
• (pm) indicates a partial hydatidiform mole, and
• (p) indicates parthenogenesis.
• (O) indicates an oocyte,
• (Z) indicates a zygote,
• (M) indicates a morula,
• (B) indicates a blastocyst,
• (E) indicates an embryo,
• (F) indicates a fetus,
• (I) indicates a live born individual person.
• (PM) indicates a partial hydatidiform mole,
• (CM) indicates a complete hydatidiform mole,
• (T) indicates a teratoma. The colors represent the maternal and paternal genetic contributions.

Footnotes

References

1. (September 2012). "The preembryo's short lifetime. The history of a word.". Cuadernos de bioetica : revista oficial de la Asociacion Espanola de Bioetica y Etica Medica.
2. Dyson, Anthony and Harris, John. [https://books.google.com/books?id=B0VJ7kYy8qQC&dq=%22Pre-embryo%22+and+warnock+and+%22New+scientist%22&pg=PA94 Ethics and Biotechnology], page 94 (Routledge 1994).
3. Steinbock, Bonnie. [https://books.google.com/books?id=ukP5IOP3iCkC&dq=%22primitive+streak%22+and+implantation&pg=PA50 “Life Before Birth,”] pages 50 and 214-215 (Oxford University Press 1992).
4. Spallone, Patricia. “Bad Conscience and Collective Unconscious: Science, Discourse and Reproductive Technology” in Rosenbeck, Bente et al. [https://books.google.com/books?id=hkkP4ogezZIC&dq=%22Pre-embryo%22+and+warnock+and+%22New+scientist%22&pg=PA131 Forplantning, køn og teknologi], pages 131-132 (Museum Tusculanum Press 1995).
5. Mulkay, Michael. [https://books.google.com/books?id=w_J-iWDDqekC&dq=%22Pre-embryo%22+and+warnock+and+%22New+scientist%22&pg=PA31 The Embryo Research Debate], page 31 (Cambridge University Press 1997).
6. Braude, Peter. [http://www.ijdb.ehu.es/fullaccess/fulltext.0104/ft607.pdf “Preimplantation Genetic Diagnosis and Embryo Research-Human Developmental Biology in Clinical Practice,”] ''International Journal of Developmental Biology'', volume 45, page 607 (2001).
7. Ashley, Benedict and O’Rourke, Kevin. [https://books.google.com/books?id=dt5CZ4vMbNcC&dq=%22Pre-embryo%22+and+twinning&pg=PA127 Ethics of Health Care: An Introductory Textbook], page 127 (Georgetown University Press 2002).