What is the management for a newborn infant born to a mother with varicella (chickenpox) around the time of delivery?

Management of Neonatal Varicella: Peripartum Maternal Infection

Infants born to mothers who develop varicella between 5 days before and 2 days after delivery must receive varicella-zoster immune globulin (VZIG) immediately after birth at 125 units per 10 kg body weight (maximum 625 units), and if varicella develops despite prophylaxis, intravenous acyclovir 10 mg/kg every 8 hours for 10 days should be initiated promptly. 1, 2

Critical Timing Window and Risk Stratification

The highest-risk period occurs when maternal varicella rash appears between 5 days before delivery and 2 days after delivery. 1, 2 During this window:

• Infants lack sufficient transplacentally acquired maternal antibody because maternal IgG antibody requires at least 5-7 days after rash onset to develop and cross the placenta. 1, 3
• Historical mortality rates reached 31% without intervention, though modern neonatal intensive care has reduced this risk. 2
• Clinical attack rate remains approximately 60% even with VZIG prophylaxis, though severity and mortality are substantially reduced. 2, 3

Infants whose mothers develop varicella more than 5 days before delivery typically have protective maternal antibody and are at lower risk. 3 Conversely, infants exposed more than 2 days after delivery face postnatal exposure risk but not the severe peripartum syndrome. 1

VZIG Administration Protocol

Immediate Prophylaxis for High-Risk Neonates

• Administer VZIG to all neonates born to mothers with varicella onset 5 days before to 2 days after delivery, regardless of whether the mother received VZIG. 1, 2
• Dosing: 125 units per 10 kg body weight, maximum 625 units. 2
• Timing: Administer as soon as possible after birth, ideally within 96 hours of exposure. 2

Premature Infant Considerations for Postnatal Exposure

For premature infants exposed postnatally (not peripartum maternal infection):

• Very premature infants (<28 weeks gestation or <1,000g birth weight) should receive VZIG regardless of maternal immunity status because they may not have acquired sufficient maternal antibody. 1, 2
• Moderately premature infants (≥28 weeks gestation) should receive VZIG only if the mother lacks evidence of immunity. 1, 2
• Full-term healthy infants exposed postnatally do not require VZIG even if their mothers have no history of varicella infection. 1

Antiviral Treatment with Acyclovir

Indications and Dosing

If varicella develops despite VZIG prophylaxis, initiate intravenous acyclovir immediately. 1, 2, 4

• Neonatal dosing (birth to 3 months): 10 mg/kg IV infused over 1 hour, every 8 hours for 10 days. 2, 4
• Treatment is most effective when started within 24 hours of rash onset. 2
• Higher doses (15-20 mg/kg every 8 hours) have been used in neonatal herpes simplex infections, though safety and efficacy for varicella are not established. 4

Monitoring After VZIG Administration

• Observe patients closely for signs or symptoms of varicella for 28 days after exposure because VZIG may prolong the incubation period by more than 1 week. 1
• Institute antiviral therapy immediately if signs or symptoms of varicella disease occur. 1

Critical Pitfalls to Avoid

Do Not Withhold VZIG Based on Maternal Treatment

Do not withhold VZIG from neonates born 5 days before to 2 days after maternal rash onset, even if the mother received VZIG. 1, 2 Maternal VZIG does not prevent fetal infection or provide adequate passive immunity to the neonate. 1

Do Not Assume VZIG Prevents Infection

VZIG reduces severity and mortality but does not prevent infection—approximately 60% of infants may still develop varicella. 2, 3 The primary benefit is reduction in complications and fatal outcomes, not prevention of disease itself. 2

Do Not Delay Acyclovir Treatment

Efficacy of acyclovir decreases significantly after 24 hours of rash onset. 2 If varicella develops, immediate treatment is essential regardless of VZIG administration. 1, 2

Do Not Confuse Timing Windows

• Maternal varicella >48 hours after delivery poses increased risk for serious neonatal complications but is distinct from the highest-risk peripartum window. 1
• Maternal herpes zoster (not varicella) during the perinatal period does not cause neonatal infection and does not require VZIG administration to the infant. 3

Subsequent Vaccination

Any infant who receives VZIG should receive varicella vaccine subsequently (provided the vaccine is not contraindicated), delayed until 5 months after VZIG administration. 1 Varicella vaccine is not needed if the infant develops varicella after VZIG administration. 1