First of all,
You've got a great adventure ahead of you and I wish you joy every moment of the whole process of considering, conceiving, birthing, caring and mothering.
While I don't think pregnancy is an illness or even a medical condition; I think the best thing is to listen to your body and your heart. If you really feel like biking (or whatever) go ahead. If you are only doing it out of habit or worse because you think if you don't use it you'll lose it... maybe think about what you might *really* like to do.
I think pregnancy is also a chance to do or try *different * things than usual and in that way it can be quite liberating. It is an opportunity to take stock. You can go over your whole life and change in the light of the pregnancy.

Women's bodies are so dynamic.....
better stop b4 the ink turns pink!