are my mice pregnant?

Question
Hi!
You said you know stuff about mice aswell so i need your advice. I brought a mouse to accompany my two females a week and a bit ago and it turns out he is male. As it's already been over a week, what is he likelyhood that my two females are pregnant? And when can i be sure that they are?
Thanks

Answer
If the male has been in there for about a week chances are very, very good that your two females or at least one of them is pregnant. You will know if they are pregnant by the way their bellies look. Their bellies will start to look round. That's one sure fired way you will know. Mice stay pregnant for about 3 weeks.