It is highly arguable. There is the parasite argument etc. But for me.. being a realist, and I don't harbor any ill feelings for anyone who thinks differently, if someone doesn't want their fetus to survive, I'm ok with that.
Anything is arguable. Potato brained morons still argue that the world is flat. People argue that there is no such thing as gender.
What I don't think we can ignore is the fact that these unwanted children would continue to grow, fall out of their mothers vagina and start walking and talking and doing all the stuff that all people do.
Except.....that at some point in the process, a doctor goes in with some tools and takes something that is alive, and makes it suddenly not alive. Also known as "killing" it.
Now if we are going to play word games and say that that baby isn't really alive then we must declare that a lot of other organisms aren't alive either. Is bacteria alive? Are plants alive? If they aren't living organisms, then what are they?