For example, there have been a number of studies that have shown that Roe v Wade is what caused crime rates to drop significantly. (Too lazy to look 'em up at this hour, but it's convincing.)
You're also ignoring concepts like nurturing, bonding and imprinting and such (again too lazy to make this somewhat accurate). The point being, almost no one misses the unknown "child" they chose to abort. Yet some people have funerals for miscarriages and such. Seems like the wanting is important in this dynamic.
I am sure there is more that could go into this discussion, but my point is that just because in most cases people who chose to keep the children they did, most often because they were wanted, doesn't mean that the unwanted children and their unwanting parents would be better off.
I'm not sure about the gestational threshold stuff, like after a certain point it's wrong.
I'm not sure about the ethics of aborting a baby that was a result of incest, rape or is found to have defects.
But I wonder if it's ethical to force an unwanted baby, because it would seem like the potential to damage two lives is worse than one on the surface. The concept that it may be better not to be born than being born into a situation without a loving and nurturing parent is real. There is also the environment this child is brought into. Edge case: would it be ethical for a malnourished, raped and impregnated North Korean prisoner to choose to keep the child (assuming they had a choice)?
These are tough questions, and no easy answers.