The Oklahoma State legislature is about to pass a law declaring "personhood" from the moment of conception, thereby making it legally a crime to harm, in any way, a fetus of any age, including apparently even at the 1-cell stage. This is, of course, simply a way for abortion foes to try once again to make abortion illegal, so that women who want to end an unwanted pregnancy will again have to go to dangerous back-alley abortionists. Never mind that a large majority of the nation supports the legal right of women to end an unwanted pregnancy.
In Oklahoma, if this law passes, a mother can presumably be jailed for child abuse or even murder if she smokes, drinks, takes drugs, engages in any sport or activity that might lead to a miscarriage, etc., etc, etc.
The Catholic Church has held this position for centuries, arguing even further that to interfere with natural conception (birth control) is to prevent a sacred life from coming into being. Expand this argument logically, and it should be a sin for any man to pass a fertile woman without inseminating her, because to do otherwise is to not allow a potential "sacred life" to come into being. And a celibate priesthood is the worst offender of all, preventing all those "potential sacred lives" from coming into being. Clearly this line of reasoning is absurd.
In fact, there is no "magic" moment when a single cell becomes a human; it is, as most things in nature are, a long, slow, complex process taking years in which the initial cell becomes "more and more" human each day, rather than there being any magic moment before which it is just tissue and after which it is suddenly human. So to arbitrarily declare, whether by religious dogma or legislative fiat, that some particular moment is the transition is absurd.
Of course logical argument really has little to do with this issue; it is really an unthinking emotional issue. Just as people can get all worked up about clubbing baby seals to death (because they are cute), but don't seem at all worried about poisoning the rats in their house (they aren't cute), so people will put their money and energy into the fight to save unborn fetuses, even while the world is awash in full human beings who are starving to death (but babies are cute, and starving, emaciated adults in Africa aren't).
At root, this is really yet another issue about controlling women. No one is worried about all the wasted male sperm that "might have been sacred humans". Nor is it the males who have to pay most of the consequences of an unwanted pregnancy. Still, one should never underestimate the absurdities than can be perpetrated by emotion and ideology.