this is a very active topic on two mtb boards I go to.

http://forums.mtbr.com/showthread.php?t=102361

http://forums.mtbr.com/showthread.php?t=105567

and here,
http://www.ridemonkey.com/forums/sho...d.php?t=123236

There is substanstial medical information that indicates it takes forces of approximately a car crash to actually damage a fetus. Studies have shown that even playing contact sports is not a problem, other than most women choose not to. More important is to pay attention to balance and heart rate issues. At some point comfort becomes an issue, so do your knees hitting your belly

http://www.insidetri.com/train/bike/...es/1486.0.html good article on racing training cycling and pregnancy

report from the Austrailan Govt' on sports and pregnanacy
http://www.ausport.gov.au/fulltext/2...ub/pisover.asp

Many women cycle sucessfully throughout their pregnancies. Of cousre the "discuss it with your doc" caveat applies. There are some old school guys out there that will tell you "no" but there are many docs out there that support active athletic women. Assuming you don't have any contraindications, go for it.

congrats.

I was off the bike by about 7 months, knees hitting the belly, to answer your question.

Irulan