Fetuses aren't human though.
If they aren't human, then what are they? They're clearly more than a random bunch of cells bonded together. 'Fetus' is not a species, it's a stage of life.
What's the argument for a fetus being a human being other than the fact that, after birth, it becomes a human being?
Hint: There isn't one, and it's not a human while it's a fetus.
If they're not human, then what species are they? Alien? This is the most ridiculous argument the pro choice people come up with. Reasonable people can differ on whether they believe the fetus is alive. But the whole it's not human thing is stupid and completely nonsensical. Sure, it's not a fully formed human. But they're still human. Just because one's brain or heart isn't fully developed doesn't mean they are a different creature from what they will ultimately turn out to be.
Weirdly, I disagree with this. Reasonable people might disagree about whether a fetus constitutes a singular instance of human life, which it does. But, no reasonable person can possibly disagree on whether a fetus is alive. That much is obvious.