I would say that cognizant autonomy is a very important factor. And I don't know when that occurs in humans. Maybe not even until after we're born.
Cognition can be lost, PureX. That doesn't make the person who's lost cognition any less human. Babies aren't autonomous even after they're born. I've watched a lot of conversations (elsewhere, not here) about abortion since the SC memo was leaked, and it's been remarkable, seeing comments like "overturning Roe v Wade will harm women across the world" and wondering do they not see the irony in that? I don't have any answers, and really don't like getting into discussions about abortion whether I agree or disagree, so I'l leave you with the point, again, that the term fetus (while scientific, I get that) isn't a term anyone uses in non-scientific settings. In everyday life, in everyday conversations among ordinary people, it's a baby. "You're having a baby!" "We're having a baby!" "This is a gonna be a big baby, you're looking at a 9-pounder at least...""Baby shower"... and of course announcements of the coming event say... "baby." The term "fetus," in conversations, is quite often, if not usually, a conscious or unconscious attempt to distance oneself from connecting "baby" with abortion.