If the rash that you are experiencing is due to an allergy, the baby won’t be damaged. But if the rash is due to some type of viral infection such as rubella, chicken pox, measles… the health of the fetus is at risk. Fortunately, your first trimester has passed so the risk for fetal damage has decreased. It is diagnose either a possible allergic reaction or viral infection without a physical examination and serological examinations. You can first see your family doctor to identify the cause for the spreading, itchy skin rash.