Several years ago we had a mouse who was pregnant when we got her. She had several babies, half of them became food for our corn snake, the other half we found homes for.

Also my chinchilla, Annie is the mother of my other 2 chins, Daphne and Lola. The lady I got them from thought she had 2 females, but one ended up being a male and Annie got pregnant. The lady was very ill and couldn't take care of the 2 chins she had and was in the process of rehoming them when Annie got pregnant. They weren't being taken care of too well and the male died. I took Annie and the 2 babies. Annie had a couple infections, Lola had a very badly injured leg (she almost lost it), and Daphne was surprisingly in pretty good health.