Certainly, if a newborn baby is entitled to legal protection, then so is a fetus a day, week, and a month before delivery. The only difficulty is identifying the appropriate stage of gestation where medical ethicists define life apart from religious presuppositions.

Modern medical technology is better capable of doing so by reference to specific biological development and neural processes, but in objective principle, the distinction of viability" introduced by the Roe Court makes logical sense.

Ethical Argument Supporting the Roe Decision:

By far, the most relevant basis for evaluating the moral argument on abortion centers on the issue of viability, except that instead of focusing on the survivability of the fetus outside the womb, it emphasizes the ability of the fetus to sense discomfort and pain, and the sufficient degree of development to support the basic perceptual functions that constitute human consciousness.

Strictly objective ethical concern would militate against causing physical pain, irrespective of whether or not a fetus was biologically developed enough to exist outside the womb; on the other hand, the mere fact that a fetus is capable of being sustained through intensive medical intervention required in all instances of substantially premature delivery would not necessarily give rise to a right to that support.

Admittedly, the idea that an organism's capability of perceiving physical discomfort or pain entitles it to protection is not a belief capable of being proved or disproved in a logical sense. Rather, it is suggested simply by the principles of human compassion and empathy. The concern against causing pain is an objective moral principle that needs no basis in religion or law. What is less clear is how that concept applies differently to human beings than to other sentient living beings equally capable of experiencing discomfort and pain.

To the extent that the ability to feel pain grants an automatic 'right" to be free from pain caused by others, animals capable of perceiving pain should also be entitled to moral concern. In fact, in many ways, even non-humans are protected to some degree by laws against animal cruelty and from being killed, even though the distinction between species entitled to protection and those not similarly entitled more often reflects cultural norms than any objective standards. Generally, we are more protective...

Objectively, the ethical concern with causing unnecessary pain does not require that the pain be experienced by a human being, so viability" of a fetus is irrelevant to moral rights of this nature (Abrams & Buckner, 1989).
Conversely, mere "humanness" by itself does not necessarily give rise to ethical

Concern either, which is a position already incorporated into medical ethics (and penal law) as pertains to indefinitely comatose patients deemed unlikely to regain consciousness. In fact, in many respects, the unconscious brain-dead patient allowed by law to be disconnected from artificial life support is closely analogous to the situation of the fetus insufficiently developed to experience consciousness, but already capable of surviving outside the womb with intensive medical support. If it is ethical and legal to disconnect a fully developed adult human being by virtue of the indefinite lack of consciousness, then it is unclear how one would justify granting rights to the early-term fetus, based merely on its being human, provided it is not yet capable of sensing pain.

Conclusion:

Instead of chipping away at the Roe decision, medical ethicists should focus on the science of more precisely identifying the point (or stage) of fetal development where abortion constitutes immoral cruelty. The fact that a fetus is human should only be considered relevant at the same point of gestation where medical intervention normally allows premature births to survive. Ultimately, that is a function of the fact that this stage is already beyond the point of sentience, not any profound significance of humanness.