Don't fall or crash. That's the biggest concern with bike riding.
Was cycling up until the end of Sept and I am due in 2 weeks. Once your pregnancy isnt causing you an issue with your balance...can't see why not. I was doing about 60-70km a week, doctor said to keep it up as long as I could because it was quiet good for lower abdominal muscles plus a low impact workout and it really did help with keeping my weight down
No reason why you cant. Especially if it was something done before pregnancy. Doctors encourage physical activity during pregnancy. Its good for both mum and baby that mum keeps active