How long does it take....

How long do you typically leave the female in with the male before you can remove her and assume she is pregnant??

I am new to this breeding thing and really didn't know this answer.

I was told they are typically pregnant for about 4 weeks - is this correct.

Thanks everyone.

A mouse gestation period is around 19-21 days, leave her in with the male until she looks obviouly prego (like she swallowed a golfball).

Like this
http://i165.photobucket.com/albums/u...se100_2161.jpg

Correct. Leave them together until she looks pregnant. Then remove the buck.