KittyJ, I bought my trio of african soft furs at a reptile show for 20 bucks. It is SOOO worth it, they smell less and compared to mice are way less prone to eating their babies.

I worked at a pet store and I often saw female mice eat other female's babies. It is pretty sick how they eat off their heads and makes a big bloody mess. I was always the one who pulled them from the display window. It tramatizes the kiddies...heh heh.
Anyways, I was always led to believe it was a mixture of stress and competition....if you are a female mouse taking care of babies and all the females are helping you, and then Jane Doe Mouse has a litter and your helpers go help her, well, Eating her litter would kind of make sense. Try keeping females seperated. I know mice work in colonies but if you are having this problem, it might just be easier to have one or two females (who get along well) per cage.