Long wait for rats to have pups, just plan a trip and they will breed like crazy

I wait and wait and wait some more for my second colony of rats to finally start breeding and having pups, don't u know it as soon as I'm to be out of town for a few days they decide to pop the pups out....... How very frustrating, the problem is that the way I have them set up is as they are ready to pop they go from large cage to tank. Well a friend is going to feed and water them but didn't want to make her deal with that part. Sry just a lil venting.......