
Even an X-ray a week before whelping when you can count the sculls and spines will not be 100%.
My friend imported a dog from the USA where the bitch was x-rayed and told five pups and 6 were born.
I have also been told by vet a bitch was empty and she passed a retained dead pup a day and a half after whelping. the fact she was unsettled and constantly straining when going for a pee they put down to the uterus contracting and bumping on the bladder.