I wasn't biking at the time I was pregnant (7 years ago), but I was playing tennis. When I started spotting in the first trimester, my doc said to quit tennis. I did. Possibly/probably it had nothing to do with anything? But again, it comes down to comfort level; if something happened, would that last tennis lesson have been worth it?

Up until the spotting incident I was given the good-to-go on tennis though. FWIW.