Of course there is a scientific reference to being viable, but you cannot take a life without considering, at least in someway, the importance of life. You cannot separate the two. If you could, then we wouldn’t have laws against murder, or a concept of justifiable homicide.
The value of life is what is intrinsically tied to this entire argument, otherwise abortion/non-abortion wouldn’t be an issue because no one would care at all. We wouldn’t care about pregnant mothers who die, and we wouldn’t care about unborn children, or very young children who die, or old people in nursing homes separated from their family because of Covid.
Without the fundamental understanding that life has a value there’s no reason to care about anyone, except for how they may happen to benefit you in the moment. We may as well be lower animals if that’s how we view life.
DD