The Unborn star, Odette Yustman, had this to say about a possible sequel...
"You know, that is quite a possibility. I know that David Goyer was talking about maybe doing a prequel. And hopefully working with Carla Gugino - she plays my mother in the movie - so maybe developing that story a little bit more and you could see why maybe her relationship with her father isn't as strong as it should be and how the real story went down. So that would be a possibility, you know, if it's a hit."
-Arrow in the Head