I had that happen with my oldest breeder. It was her last litter before I was gonna retire her. She pushed out 18 and I didn't see it until 2 days later whe she was leaving pups all around the tub. I picked her up and found it. Her entire rear was a hole. I tried to pull it out because I thought it might have been a pup that got stuck. Part of it pulled off. I couldn't stand to look at her like that, so I put her down immediatly after that. The pups were all being nursed. She really was a super mom. Ended up only nursing three off on to another mom.