As Ginge says - if you're thinking this then maybe your not with the right woman.

But...is there not a chance this could just be a phase due to not getting enough attention from your wife because she is pregnant? Think about what you stand to lose here, and how F*cking terrible this will make your wife(who probably loves your more than anything) feel. And what about all the happy times and things you have been through with your wife...and the way she has made you feel.

Just have a good think about it mate, before you rush into anything.

sorry for my very serious reply, but i've been on the recieving end when its been the other way around(girlfriend betrayed me big time).