What Precautions Can A Pregnant Take To Avoid Scarlet Fever ?

Hello, my 3 years old daughter has scarlet fever and is currently being treated with azytromicin (20 mg/kg/day, during 3 days). She is responding well. However, I am more concerned for my wife. She is 4 weeks pregnant and has been in close contact with our daughter. Is there any precaution she should follow, for example take penicilin as a preventive measure? I m worried because she is in early pregnancy , so it is difficult to decide what carries greater risk - penicilin in early pregnancy or bacteria . Is it sufficient just to follow her condition in order to act swiftly in case she develops sore throat or rash? Thank you for your answer.