Continuity Argument
According to the continuity argument, the development of an embryo into a born human being progresses so continuously that it is impossible to distinguish clear-cut breaks that could then be used to justify a change in moral status. The dignity of a grown person therefore also goes back to the early embryo and, according to this argument, must be afforded to the early embryo.
Different Positions can be found in:
Holm, S. (1996). The Moral Status of the Pre-Personal Human being. The Argument From Potential Reconsidered. In Evans, D. (Ed.). Conceiving the Embryo. Ethics, Law and Practice in Human Embryology. Brill | Nijhoff. https://doi.org/10.1163/15718099720522066
Singer, P. & Dawson, K. (1990). IVF Technology and the Argument from Potential. In Peter Singer et al. (ed.), Embryo Experimentation. Ethical, Legal and Social Issues. Cambridge University Press.
Ford, N. M. (1988). When did I begin? Conception of the human individual in history, philosophy and science. Cambridge University Press.
Brock, D. W. (2006). Is a consensus possible on stem cell research? Moral and political obstacles. In Journal of Medical Ethics 32(1), 36-42. https://doi.org/10.1136/jme.2005.013581
Strong, C. (2006). Preembryo Personhood: An Assessment of the President’s Council Arguments. In Theoretical Medicine and Bioethics 27(5), 433-453. https://doi.org/10.1007/s11017-006-9016-7
Mauron, A. & Baertschi, B. (2004). The European Embryonic Stem-Cell Debate and the Difficulties of Embryological Kantianism. In Journal of Medicine and Philosophy: A Forum for Bioethics and Philosophy of Medicine 29(5), 563-581. https://doi.org/10.1080/03605310490514234