I have had 2 babies while working on tele floor and taking all kinds of isolations except for chickenpox. Never had a problem.
I am now pregnant with my 4th child and working in ER and really am not worried about it. You could be exposed to all of those types of people in the local grocery store, coughing and hacking all over you. At least as a nurse, you know something is wrong with them. Use your standard precautions, and if someone seems suspicious for some contagious disease, use more protective gear.
Tell the charge nurse you won't take certain pts if you are uncomfortable with caring for them. I have found that co workers are usually looking out for me, but if they don't, I just let them know.
Good luck. Try not to worry too much, enjoy your pregnancy.