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In human embryonic development, a preimplantation embryo is an embryonic stage before it becomes implanted in the uterus. The term pre-embryo previously put forward as an alternative has fallen out of use.
Implantation begins about six days after fertilization, and lasts for about a week, during which time formation of the primitive streak occurs.Steinbock, Bonnie. “Life Before Birth,” pages 50 and 214-215 (Oxford University Press 1992).
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.Spallone, Patricia. “Bad Conscience and Collective Unconscious: Science, Discourse and Reproductive Technology” in Rosenbeck, Bente et al. Forplantning, køn og teknologi, pages 131-132 (Museum Tusculanum Press 1995).Mulkay, Michael. The Embryo Research Debate, page 31 (Cambridge University Press 1997).Braude, Peter. “Preimplantation Genetic Diagnosis and Embryo Research-Human Developmental Biology in Clinical Practice,” International Journal of Developmental Biology, volume 45, page 607 (2001). 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.Ashley, Benedict and O’Rourke, Kevin. Ethics of Health Care: An Introductory Textbook, page 127 (Georgetown University Press 2002).
The colors represent the maternal and paternal genetic contributions.
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