It sounds like something pre-existing was going on to do that, wether she knew about it or not? I have not heard of a baby breaking a pelvis before, but it's hard to really know without more info. You hear big babies with the label of getting 'stuck' if they are 'too big' but I have not heard of a baby causing such a thing prior to this. But like I say, need to know more medical information to make a comment... pelvic bones are strong, a baby couldn't easily break them. I am not saying you aren't telling the truth - just sounds very strange - and painful! Nothing could have predicted that happening and I wouldnt suggest to have a caesarean 'just in case' as they do have higher risk than a vaginal birth.