Lets say your driving above the speed limit when you don't have too for pleasure (like people have sex when they don't have too for pleasure). Lets say that you end up accidentally running someone over while driving above the speed limit and the only way they will survive is if you give them a kidney. Lets say they were in a cross walk so they were crossing the street legally.
This analogy presents the fact that if you didn't screw up, somebody wouldn't be needing you for help (just like with pregnency/recreational sex/abortion). If I did this to someone and they needed my kidney, I would absolutely oblige since I screwed them up, I would feel a personal obligation to save their life since I caused them to be dependent on me. However, forcing OTHERS to oblige if they are in a similar situation seems too authoritarian to me. You SHOULD save the person that you caused to be dependent on you, but it's not an obligation.
I have to treat an unborn baby the same way up until the moment of birth. I'm not proud of this, but I have to be consistent.