Hi there, or you could just change over to Cortef (hydrocortisone) instead of dex. Cortef does not pass the placenta.
Are you taking Dex for locah?
If you take a low enough dose of Cortef it should not supress your immune system. Most people however require a slightly higher dose during pregnancy anyway. I myself weaned off of .75mg of Dex with my son and I don't really remember anything particular happening but I was extremely emotional (CRAZY) during my pregnancy with him. I had been on Dex for a little over a year I think.
Now after I was on Dex for many more years I suffered from fatigue anytime my dose was altered and I had to wean down. I also became very weepy and emotional. I was not pregnant.
Well that's my experience. Good luck! Congrats on the baby boy!