My mum is shorter than 5' and one of my brothers was 10lb when he was born! So while there might be some kind of link, there's always exceptions. Oh, and he was delivered naturally with no interventions

ETA: I'm a firm believer that your body doesn't grow a baby that you can't give birth to (provided you have the right support, info, etc). If nothing else, it doesn't make sense for survival of the species (ie. us!) if we grow babies we can't birth...