Found this, hope it helps.
Mice breed very fast. The average litter is about six to eight kittens (baby mice). Males and females should be separated at around three weeks after a litter is produced otherwise the female will become pregnant again
And....
males can be kept with the females after the babies are born as they will not harm the young (and often actually help to babysit!).
When baby mice are born they are deaf, naked, and blind. Within two weeks the babies will look just like their parents, just smaller. They may be weaned in approximately five to six weeks.