
Hi Sophie, it will probably be any time in the next 2 or 3 months. You will notice that she scent marks with urine for a week or so beforhand, and your boy will be very interested in the spots that she has urinated on. He could well be your early warning system. It might be an idea to make sure they cannot get to eachother over night and when you're out from about now. Could one of them prehaps sleep in a large crate? It might be wise to do a quick daily check on her vulva, to see when any swelling starts to become noticable. You might also want to get a copy of 'The Book of The Bitch' it's available from Amazon.
Dawn R.