Board Thread:New on Creepypasta Wiki/@comment-5946346-20130103192036/@comment-5643552-20130107015212

It's a very psychological pasta. It plays on a new mother's attachment to her baby - or in this case, baby doll - and how that attachment can blur her perception of reality. She comes to take care of the baby doll for so long that doing this (beating it to shut it up) becomes second nature, and she reacts without thinking. So, by the time the actual baby is born, her attachment to the doll has blurred her perception of reality to the point that she confuses the it with the actual baby. So, naturally, when the baby starts crying and making noise (as all babies should), and since beating up the doll has become second nature for her, she reacts without thinking.

Anyway, that's how I interpreted it.