Most philosophers and bio-ethicists do not recognize any moral problem with abortion before the stage of fetal development where a brain and nervous system form because they are necessary for sensory perception and the fetus is incapable of feeling pain at that stage. Still, philosophers are concerned with when a clump of cells becomes a person, irrespective of sensation, or else aborting fetuses at eight months would be permissible as long as it was anesthetized first. Clearly, apart from religious beliefs and sensory perception, a nearly fully developed fetus may no longer be aborted morally; but just as clearly, a very recently fertilized zygote does not create a moral obligation to carry it to full term to be adopted instead of being aborted shortly after conception. There is no precise instant where a fetus makes an instantaneous transition to sentience; nor does it suddenly acquire all the attributes that makes it a person either.
Rather, both occur gradually and components...
Nevertheless, biologists do understand the fetal developmental process enough to define stages before which sentience is impossible, and before other attributes of personhood develop because the necessary anatomical structures are not yet formed. Since those definitions allow for erring on the safe side of any "grey" areas of uncertainty, aborting an unwanted
pregnancy before that stage of development is morally permissible, and pregnancies beyond that stage may not be terminated through abortion without moral justification, such as medical necessity for the
mother. Beyond that, adoption is the moral choice.
References
Dershowitz, Alan, M. (2002) Shouting Fire:
Civil Liberties in a Turbulent Age. New York: Little Brown & Co. Abrams, Natalie, Buckner, Michael, D. (1990) a Clinical Textbook and Reference for the Health Care Professions. Cambridge: MIT Press
