To be clear, you are right that a late term abortion is pretty horrific. They're also -traumatic-. No one is -intentionally- waiting around to get an abortion; there isn't room for political argument here because anyone who finds themselves pregnant at a late stage and doesn't want to be is already in the case of "reasonable exception". A medical complication, a change in financial status to where she can't support it (when before she thought she could), etc.
No one is finding out they're pregnant in the first trimester, and then just can't make up their mind until the third, and we as a society need to set a date she has to make up her mind, or force her to keep it against her will. That's a made up justification, and as we continue to see, the same forces that make that justification don't even stop there.