**Core Concept**
Varicella zoster virus (VZV) infection in pregnancy poses a risk to both the mother and the fetus. The risk of congenital varicella syndrome (CVS) is highest when the infection occurs between 13 and 20 weeks of gestation. Maternal antibodies against VZV are crucial in preventing severe disease in the fetus.

**Why the Correct Answer is Right**
In the absence of maternal antibodies, the risk of severe varicella infection in the fetus is high. Varicella infection in pregnancy can lead to CVS, characterized by limb hypoplasia, cutaneous scars, and central nervous system abnormalities. The correct management option is to administer varicella zoster immune globulin (VZIG) to the pregnant woman as soon as possible after exposure. VZIG provides temporary protection against VZV infection by neutralizing the virus.

**Why Each Wrong Option is Incorrect**
**Option A:** Acyclovir is an antiviral medication that can be used to treat chickenpox in pregnant women, but it is not the best option in this scenario. Acyclovir can help reduce the severity and duration of the disease, but it does not provide the same level of protection as VZIG.
**Option B:** Corticosteroids may be used to reduce the risk of preterm labor and fetal distress in pregnant women with chickenpox, but they are not the best option in this scenario.
**Option C:** There is no benefit in administering varicella vaccine to a pregnant woman exposed to chickenpox. The vaccine is not effective in preventing disease in previously unimmunized individuals, and its use in pregnancy is contraindicated.

**Clinical Pearl / High-Yield Fact**
Varicella zoster immune globulin (VZIG) is a lifesaving intervention for pregnant women exposed to chickenpox without maternal antibodies. It should be administered as soon as possible after exposure to reduce the risk of severe disease in the fetus.

**Correct Answer:** C.