Yes, this behavior is perfectly normal. When I have a litter of pups I spend a lot of time letting the mom in and out. The moms like to spend a lot of time in the living room once the puppies start getting a bit older. The older the pups get the more time the mom will want to spend away from them. I always setup my x-pens so mom can escape the pups when she wants too. I have a board that I put across one end of the x-pen and it will contain the pups usually until they are at least 8 weeks old or older, depending on their size. I have attached a picture of my setup. At night I leave the mom with the pups but she is still able to able to escape them. The mom has bedding, food, water and pee pads on her side of the x-pen also. It is a lot of work trying to keep everyone happy.
