I agree you will have to wait to see what your body says. Many Doc's don't recommend cycling while pregnant for the reason of falling. I lost my first child possibly from mountain biking during my first few weeks. During my second pregnancy I was able to ride into about my 7th month. I had to stop mostly because of lung capacity, I just felt I couldn't ever catch my breath. But I toned it down and remained on the road or the bike trails and laid up my mountain bike for 10 months. I was able to continue to ride 3-4 hours in the begining to about 1hr at the end. I do strongly encourage you continue to excersie in some way during your pregnancy. And if its cycling you love then thats what will keep you motivated to continue to keep fit. I truly feel it helped me get through. Best wishes on a healthy pregnancy.