First off, congratulations!! So exciting and don't say it is stupid of you to get pregnant. Unfortunately, the perfect, healthy period doesn't really exist when you have Crohn's so you have to do it sometime.
I am 11 weeks pregnant right now. I had a bad flare up in week 9. My doctor has put me on 30mg of pred a day. It has helped tremendously. At first I was apprehensive but within two days I was feeling better. I honestly don't know how I would have survived without it. I did a ton of research and everything came out that prednisone is well studied and carries very little risk. I spoke to MotherRisk which is an organization that only looks at drug studies and pregnant women. They said there is a very slight chance of oral cleft in the baby but it is only 2 in 1000 vs. 1 in 1000 for any random pregnancy. They said it was a "Safe" drug for pregnant women.
Don't worry ( I know it is so hard not to). I have had some very rough episodes and even went to the hospital during my flare in week 9 and actually saw the baby moving around. i think they are a lot tougher then we think. Take good care of yourself and best of luck with everything.