I am someone who has been pregnant while dealing with Crohn's/Colitis (doc isn't sure exactly which one). I have used prednisone, salofalk suppositories and more recently Humira in my last 2 pregnancies. So, me and my babies have been "guinea pigs" to some degree. I think prednisone was the worst of the ones I mentioned. I guess I am just saying, from my point of view, do what you need to do to keep you healthy so you canbw an awesome mom for your baby!
During my second pregnancy I flared up around 15 weeks and I tried some mild supplements which didn't help. Finally at 20 weeks I got on prednisone which helped....but then I couldn't wean off without the blood coming back with a vengeance. Oh dear, just remembering it is brutal. So good to be on the other side. = ) Anyway. At 30 weeks I was desperate and finally was in the dumps enough to try a drastic diet change. I began Elaine Gottschall's Specific Carbohydrate Diet (SCD). It helped so much I went down to a very low dose of prednisone for the rest of the pregnancy. I am a huge fan of the SCD. Don't let anyone tell you that diet can't help (a lot!!) with IBD. It hasn't singlehandedly cured me, but it's probably 40% of why I have been in remission for 2.5 years. I would only give Humira maybe 20% of the credit (it doesn't fully work either, if I mess up on the diet I feel it!! It's not such a wonder drug that I can eat whatever I want!). The other 40% is spiritual and emotional healing in the way of anger, anxiety, stress...too complex to explain here, but God's been working on me. ; )
So congrats on your baby growing within, these are exciting days! Carefully weigh your options but don't live in too much fear because a particular drug hasn't been tested in pregnancy. I had to take a few risks but I have healthy (so far!) wonderful children. You will know in your gut what's right. It IS a little maddening, though, the lack of research which forces us to guess!