I, too, was faced with this same situation when I returned to work after being off for 12 weeks in my pregnancy.
Before I returned to work, I asked my OB what rooms I needed to stay out of-people with shingles (varicella), etc. He told me to stay out of ALL isolation rooms-he said "anyone that is pregnant does not need to be in those rooms."
I had to put up with the comments my co-workers made too-"well you have already been exposed to it..yadda yadda yadda" I stood my ground with my nurse manager and my co-workers...Anytime they complained about my NOT going in these rooms-I told them they could call my OB and talk to him..
...shut them up pretty quickly
It didn't help matters any that there were 2 other co-workers that were pregnant at the same time as me...they did go in isolation rooms..I had to keep telling them that I was following MY doctor's orders.
The health of you and your unborn child is more important than what comments your co-workers make.