I had two easy pregnancies, and in both cases my Ob/Gyn told me no cycling. I was sure it was silly machista advice from someone who just wasn't used to active patients (I'm in Chile)... but I took his advice anyway and did not cycle during either pregnancy. I needed to know that I was doing everything I could to ensure a safe, healthy pregnancy. For activity, I really enjoyed hiking with my dogs. It was not as active as I was used to, but it satisfied my need to get out and get moving.