Congenital Varicella

Introduction And Epidemiology

Varicella-Zoster Virus (VZV) causes chickenpox and can lead to severe complications in the fetus and neonate.
Varicella infection during pregnancy is uncommon, occurring in about 3 in 1,000 pregnancies.
Primary transmission occurs through respiratory droplets, contact with vesicular lesions, or transplacental transfer.

Congenital varicella syndrome occurs when maternal infection happens early in pregnancy.
The risk of congenital syndrome is low, estimated at 0.55% during the first 12 weeks of gestation.
The risk increases slightly to 1.4% when maternal infection occurs between 13 and 20 weeks of gestation.
Fetal death or early neonatal demise may occur.

The greatest risk for severe, life-threatening infant disease occurs when the maternal rash appears between 5 days before and 2 days after delivery.
This timing provides insufficient time for the fetus to acquire protective transplacental VZV-specific antibodies from the mother.
Neonatal symptoms typically begin 5 to 10 days after delivery.
The expected mortality rate in this high-risk window is approximately 30%.
Severe complications include hemorrhagic pneumonia and necrotizing hepatitis.
Postnatal varicella acquired from exposure after birth is generally mild if maternal antibodies are present, but it can rarely lead to severe disseminated disease.

Diagnosis is primarily clinical, based on a typical vesicular rash and a maternal history of peripartum varicella or postpartum exposure.
Laboratory confirmation involves detecting the virus from cells at the base of a vesicle.
Diagnostic modalities include Polymerase Chain Reaction (PCR) and immunofluorescent antibody testing.

Infants with congenital infection from early in utero transmission usually lack active viral disease at birth, so antiviral therapy is not indicated.
Symptomatic infants with severe disease must receive Intravenous (IV) Acyclovir as soon as possible.
Severe disease includes pneumonia, severe hepatitis, or presentation with more than 50 rashes.
The recommended dose of IV Acyclovir is 30 mg/kg/day divided into three doses for 7 to 10 days.
Oral acyclovir is not recommended for symptomatic neonates because of poor enteral absorption in this age group.

Varicella Zoster Immunoglobulin (VARIZIG) or Intravenous Immunoglobulin (IVIG) provides passive immunity and reduces the risk of severe infection.
The dose of VARIZIG is 125 IU for infants weighing less than 10 kg, administered intramuscularly.

Exposure Scenario	Prophylaxis/Treatment	Additional Management
Maternal rash 5 days before to 2 days after delivery	VARIZIG or IVIG within 48 to 96 hours.	Isolate dyad. Separate mother and neonate until maternal lesions crust.
Preterm <28 weeks or <1000 g birth weight	VARIZIG or IVIG within 48 to 96 hours, regardless of maternal history.	Strict infection control and isolation.
Asymptomatic newborn exposed to infected person (not mother)	VARIZIG or IVIG within 48 to 96 hours.	Observation for symptoms.
Infant <1 month presenting with clinical signs (high-risk setting)	IV Acyclovir for 7 to 10 days, ideally within 24 hours of rash onset.	Assess for severe disseminated disease.

Airborne and contact infection control precautions must be strictly implemented.
Isolation continues until all lesions have crusted, which usually takes at least 5 days.
Breastfeeding should be continued because protective antibodies pass through breast milk.
If the mother and baby are separated due to active maternal lesions, expressed breast milk can be provided unless there are active lesions directly on the breast.