I agree with Mark. Everyone likes a big square hip on a heifer, but make sure the pin bones are situated slightly lower than the hook bones, as this will allow her to calve easier. I think many of the calving issues we hear about, that are blamed on the sire used, could be blamed on the female that calves. I guess we shouldn't even blame the female, as she was designed the way she was by breeders trying to design show ring appeal, as opposed to functional appeal. Take a look at other animals in nature and see how they are designed. Have you ever heard of a deer, antelope, elk, etc, that could not give birth easily? As I mentioned before in another thread, Brahman cows are also designed with more slope between the hooks and pins and they can calve extremely easy, no matter what size the calf is.
As Mark has said, you can also have breeding problems when the hooks and pins are situated too level.