Hey
I also work in a hospital with Swine flu patients- although I am not in contact with these or any patients.
I spoke to my Ob last night about it, think (hoping rather!) that he suggest I not work there for a while hehehehe!
He explained that even wearing a mask does not reduce your risk of catching it, there is more of a chance of catching it by contact, for example, someone with the infection touching a desk, then you touching the desk later on. Then touching your face mouth nose etc.
He just told me to be more careful about hand hygeine, wash often, use anti-bacterial hand sanitisters (even the ones that you dont use with water are fine).

Also, maybe you could speak to your doctor about getting the antibiotics for the 'just in case' as they are safe while pregnant.
I would still go, but thats my opinion. Just need to be a bit more careful than normal!