I have vague memories of reading this in the 90s. It was a paperback, possibly an R.L. Stine book (it seems like the right sort of plot and I have this vague memory of it being similar cover art). The main character is a girl who's pregnant. She and her boyfriend go to an abortion clinic (a legal one, not back-alley). That's where things get a little jumbled in my head. I remember the girl bleeding out on the operation chair due to a botched procedure. I also remember her and her boyfriend being stalked by a girl of the same age including a part where the protagonist gets stabbed through the stomach with a pitchfork. I want to say that the sequence of events was that they got stalked by the girl, she got stabbed, and the scene then cut to her bleeding out on the chair with the implication being that it was either just a dying dream, or that the girl who killed her was the unborn baby trying to get revenge.
The reason I see it as either sci-fi or fantasy was that the scene played out like a nightmare where no matter where they turned, their pursuer was behind them with the scenery changing malevolently against them. I want to say that they died a few times during the story, each time with them waking up from a seeming nightmare only to get killed again in a different way.