Of course there are risks with everything. Maybe I'm a clutz, but I've tripped walking a lot more times than I have fallen off my road bike. And I agree, I think driving is more risky than riding.

There's also tons of articles/studies supporting road cycling and jogging for the duration of the entire pregnancy. It helps prevent pre-term labor, miscarriage, prepares your muscles for delivery, and helps prevent pre/post-partum depression.

I recommend finding an OB/GYN that works out. I was fortunate enough to find one that runs marathons. She keeps up on all the latest studies regarding exercise and pregnancy because it's important to her. She also has a better understanding of my fitness level and what I am healthfully capable of during pregnancy. She's been wonderful.