Is my mouse Pregnant?

Question
I am doing a science project on Breeding mice and i was wondering if you could somehow tell if the mice are pregnant? i know after what...a month something is supposed to happen but its been since October 15 and nothing has happened.  do you know why??  

Answer
If she were pregnant she would have had them by now.  The gestation period on mice is 19-24 days.  She may have been too young (under 12 weeks) or too old (over 9 months) when you bred her so you may need to try again.  Also, if a male other than the one she mated with was left in the cage with her she may have aborted the fetuses to save them from being killed.  Even the male she mated with should be removed no later than 2 weeks after they mate.  You may need to try to breed her again.

Let me know if I can help with anything else,
Lauren