I managed to bike until 22 weeks pregnant.  My OB wanted me to stop at 20 weeks, but I felt great, so I continued a few more weeks.  Reluctantly, at 22 weeks, I decided it was time to stop, even though I was still enjoying it.  However, biking it until 5 1/2 months still seemed like quite a feat.  Now I’m working on developing a new workout routine.