Strep throat (if you get it) isn't dangerous to the baby. I don't know of any ways to prevent it, but if you get it you can take to your doctor about safe antibiotics, or ride it out. There are a few things you can do to soothe the pain if you choose to not take medications for it and such.
I got scarlet fever while pregnant in 02 I think you will be ok if you feel as though you have it go to the dr for antibotics :)