When Zoe had her pups, she would go out to potty and sneak off and start digging a hole! I swear she thought she was going to take them outside and put them in that hole!
She was so focused on the pups at that time that I knew it had something to do with them. Anyways, I made sure I gave her plenty of calcium - cottage cheese, whelping pudding - and after a week or so she settled in and things were fine. But I would keep a close eye on her and make sure she can't move them.