I would talk to you ob-gyn. Some OBs are OKAY with you riding, others are not. When I was pregnant with my son my ob said absolutely not. Too much risk of falling off, even my steady-eddie. I also would have felt horrible had something happened, so I didn't ride at all during that pregnancy. With my daughter I wasn't riding much anyways when I found out, so I just stopped riding. Good thing too because I had pre-term labor from 29 weeks on and was put on bed rest the last third of my pregnancy.
I personally wouldn't have chosen to ride even if my obs had said it was okay, or if I weren't high risk. But if you are comfortable with it, you aren't high risk, and your ob okays it, then go for it (gently).
Just remember that your center of balance shifts DRAMATICALLY while pregnant. I still find four months after the birth of my second child that my balance is completely off and everything has shifted. I'm beginning to think it's permanent
Oh and congrats!!!! Children are wonderful blessings!