My dog is going to have puppies !?

my dog is a kc reg staff and the male is kc reg bull mastiff i was wondering if because of the size of the bull mastiff will this cause problems with the birthing of the puppy's so shorter .....will my dog struggle to give birth to the puppies ? if i get a good solid answer that i want from the questions i will choose that as best answer i do not want answers saying DO NOT BREED THEM thanks !