Don't worry- mice only have 5-6 babies per litter
yea, but they have them every 2 months!
Wrong... mouse can have 10-12 babies by litter... gestation period is 20 days... the female having give birth is fertile again 14-24 hours after having give birth... if there is lactation, the new fertile eggs have implantation delayed of 3 to 10 days... so, in the best situation, you can have around 150 babies year, more if you count that female are ready to reproduce after 25-40 days and males after 50 days...
Sometime ago, i have catch a mouse who was sleeping each night at the top of my hamster cage, moving each night piece of old newspaper who was used below the cage for catch the hamster dirt... Having catch the mouse, i have put it with the hamster... now, i have 10 young mouse in the cage... hope that they cannot reproduce between brother-sister-mother !!!

Now, the kids of my girlfriend find the baby mouse cute... and my girlfriend have forbid me to trow them away !!!