Shingles and chicken pox are actually the same thing. Both are caused by the Varicella-Zoster Virus (VZV), a type of herpes virus. Chicken pox is the initial infection. After the skin heals from the pox marks, the virus retreats into the nerve roots of the spine and can migrate back out years later to form an irritating rash called “shingles.” The fact that the lesions are later distributed along parts of the body supplied by particular nerve routes helps in the diagnosis. Both forms of VZV are contagious, and if exposure is within the household, non-immunized individuals will more than likely get it (probably as chicken pox).
In pregnancy, chicken pox is extremely dangerous, both because it’s dangerous in adults anyway and because pregnancy alters the immunological strength of the expectant mother. Varicella pneumonia is the complication that is feared, and such a complication can even lead to death!
I recently had a pregnant patient who was VZV non-immune. I told her to stay away from Christmas shopping, crowds, theaters, etc., because for any crowd there’s got to be some VZV floating around. Risk to the baby is more likely if infected in early pregnancy than late. If exposed, VZIG (antibody shot) should be given if less than 20 weeks pregnant. Certainly before or after a pregnancy, VZIG should be given to immunize women of childbearing age.
In prenatal emergencies with VZV, the antiviral drug acyclovir, the same thing given for genital herpes, can be used in large doses. So far there is no evidence that acyclovir hurts the baby, and because it’s been around for a while, that’s a meaningful safety record.
Regarding your question: You need not stay away from people with shingles or chicken pox if you’re immune. Your doctor can do a simple blood test to tell whether you’re immune or not. If so, you’re OK. If not, ask your doctor about immunization if you’re in early pregnancy.