things changed with my small group of friends once we told them we were expecting. We just gradually had less and less to say to each other and now I don't talk to them at all, maybe here and there on facebook but haven't seen any of them IRL for a long time.

I do have a few friends from my old work that I keep in regular contact with and see occasionally as they have kids around DD's age. I'm very thankful for them because I don't have anyone else- we moved towns and haven't had much luck finding new friends here.

I think if your friends are still a little immature then your social group kind of needs to change now that you have a child, they just simply don't understand what it's like. Great if they are supportive and understanding and still make the effort, but if they aren't then it might be best to cut your losses and find some 'mummy friends'. If and when they want to grow up and be real friends to you then welcome them back into your life. It is hard though.