I wouldn't say I'm a RUNNER, but I've been running lately. I'm doing some sort of heavy exercise at least every MWF, and we usually take at least one hike on the weekend. Running has been okay, better if I'm not pushing the jogging stroller.
I know women who have run, downhill skied, and bike through their whole pregnancy (not all three---just one for each particular woman), and the key really seems to be consistency. If you are doing something every day, then your body slowly adapts to the changing shape and center of gravity of its new self. But if you didn't bike for a month or so, you'd have a much higher chance of falling because you wouldn't be used to the "new you", know what I mean?
I don't really bike enough to keep it up, nor will there be enough snow around past July to make it back to winter, but I DO intend to keep running this time. I was VERY active with my first pregnancy, but I didn't run at the time (just eliptical machine, fast long walks outside, hiking, snowshoeing, etc). This will be a cool change!
Mama to DS 3/05 and DD 1/08