I think yes a visit to the vet for an xray may be in order. Im not sure what questions you have specifically but here is a site that may be helpful:
Canine Reproduction Video and Book on Breeding and Whelping dogs by Debbie Jensen for dog breeders and Whelping Supplies needed to deliver puppies.
I hope that you are fully prepared for anything and everything that could go wrong. Its always best to be prepared than to be caught off guard and not know what to do. Be sure that you have your vet and the emergency after hours vet on speed dial.