Hi Txarmywife,
Your doctor is probably trying to quiet your immune system using a prednisone (prednisolone) burst ranther than doing a long course protocol with the taper because you are pregnant. Prednisone is a Pregnancy Category C drug. This means:
from the wiki ".... Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks."
It is not advisable to use prednisone in pregnancy unless it is really necessary. But, studies have shown a Crohn's flare is more harmful to the fetus than a short course of steroids. Also, prednisolone is less able to cross the placental barrier than some other steroids.
Also problematic with a flare during pregnancy is the increased likelihood of dehydration. Since you are having vomiting plus diarrhea you are losing a lot of liquids.
Make sure you are getting enough vitamins especially folic acid. You may want them to check your vitamin levels (when you are finally seen).
I checked on your antibiotic. Cefdinir is a Pregnancy Category B, which basically states that there was no increased risk to the fetus in animal studies but there is not enough data in humans to consider the drug "safe" for pregnant women. [wiki]Pregnancy Categories for Drugs[/wiki]
Cefdinir Antibiotic
How long do you have to wait to see the GI? It is highly recommended to be monitored by your GI in concert with your OB / GYN because of increased risk to the fetus during Crohn's flare.
I really hope you are seen soon......
IBD in Pregnancy:
http://www.wjgnet.com/1007-9327/pdf/v17/i22/2696.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2693677/pdf/WJG-14-1326.pdf