Congrats Drtgirl!
I wish I'd seen this at the time - I faced the same dilemma two cx seasons ago, and decided to ride but not race. Even though I am super-slow, I have definitely crashed, and I especially didn't want someone else to crash into me. I do recommend riding throughout the pregnancy if you're able. It was great for my joints, kept my weight down, and I had a very smooth and fast recovery.
I made vague health-related excuses, and then my "reveal" was timed to our local Halloween race...I dressed up and rode as "a bun in the oven". Very fun!

I keep getting sick in the fall since I've had my son (now almost 20 months) so I haven't gotten to race as much as I'd like. Still, it's great fun when I do!

Best of luck with the rest of your pregnancy!