What Are The Effects Of Using Betadine Mouthwash During Pregnancy?

Hi! I am 39 weeks pregnant and have a nasty upper respiratory infection with some pustules in my throat. I am on antibiotics (amoxicillin) and was also recommended to use betadine mouthwash as a gargle. I have been reading that betadine should be avoided by pregnant women. I used it once but am nervous to use it again. Should I avoid it? Will the one time use have a negative effect? Thanks for your help!