From my few hatches what I understand is they rest after breaking through. The first pip through must be the hardest. I have helped on a couple after it went past 24 hours and I saw the the beak was protruded and the chick gasping for air. Both times they were LARGE chicks and seemed to not be able to move in the shell. I lost one silkie under a broody hen because I did not know when it had pipped and assumed it would get out. Before burying I took it out of the shell and it was a large chick that had completely filled the shell and no air space to move. I assume that when it could not get out it grew into the shell to the point of suffocating.