This one is really up to you (as far as after transfer). I can tell you what I did, but you may want to approach differently. First, I've had four losses in the first trimester and whereas I don't think anything would have changed that, had I been running I would have questioned whether that contributed. I didn't want anything on my conscience. I ran or worked out as normal leading up to the transfer and then switched to walking or less strenuous exercise. In my pregnancies, the sickness kicks in at 5ish weeks and walking is about all I can do then anyway. When I start feeling a little better (second trimester) I start running again, and am just careful to listen to my body.
Good luck!