What is the recommended management of chickenpox (varicella) in a pregnant woman, including treatment for symptomatic infection and prophylaxis after exposure?

Management of Chickenpox (Varicella) in Pregnancy

All seronegative pregnant women exposed to varicella must receive varicella-zoster immune globulin (VZIG) within 96 hours of exposure to prevent severe maternal complications, and if chickenpox develops despite prophylaxis, oral acyclovir 800 mg five times daily should be initiated within 24 hours of rash onset. 1

Post-Exposure Prophylaxis for Seronegative or Unknown-Immunity Pregnant Women

Immediate Assessment

• Obtain varicella-zoster IgG serology immediately for any pregnant woman with possible exposure, because a history of disease is unreliable; immunity is considered present if the woman has documented two-dose varicella vaccination, laboratory-confirmed IgG positivity, or a health-care-provider-verified history of varicella or herpes zoster. 1
• If serology is negative or results are unavailable within 96 hours of exposure, administer VZIG as soon as possible. 1

VZIG Administration

• Recommended dose: 125 IU per 10 kg body weight, not to exceed 625 IU, given intramuscularly. 1
• Timing is critical: VZIG should be administered ideally within 96 hours of exposure, though administration up to 10 days post-exposure still confers benefit. 1, 2
• Effectiveness: VZIG reduces the incidence of varicella infection in exposed pregnant women from >70% to approximately 30% and markedly decreases severe outcomes such as pneumonia. 1
• Important limitation: VZIG prevents severe maternal disease (e.g., pneumonia) but does not prevent maternal viremia, fetal infection, or congenital varicella syndrome. 1

Alternative Prophylaxis

• Oral acyclovir prophylaxis can be considered if VZIG is unavailable or if exposure occurred >96 hours ago. 1, 2
• If oral acyclovir is considered for prophylaxis, perform VZV IgG serology so that the antiviral can be discontinued promptly if the patient is found to be seropositive. 1

Post-Exposure Monitoring

• When VZIG is given, monitor the mother for prodromal symptoms (fever, malaise, headache) and the characteristic vesicular rash for 28 days after exposure (extended from the usual 21 days because VZIG can lengthen the incubation period). 1
• If VZIG is not administered, monitoring should continue for 21 days. 1
• If any signs or symptoms of varicella develop, institute antiviral therapy immediately. 1

Treatment of Active Varicella Infection in Pregnancy

Maternal Risk

• Pregnant women are at higher risk for severe varicella and complications, particularly pneumonia, compared to non-pregnant adults. 1

Antiviral Therapy

• For pregnant women at increased risk of moderate to severe varicella, oral acyclovir 800 mg five times daily should be initiated within 24 hours of rash onset. 1, 3
• Treatment duration is 7 to 10 days. 3
• Acyclovir is most effective when initiated within 24 hours of rash onset. 1
• Acyclovir does not reduce transmission of varicella or duration of illness, but reduces severity of symptoms. 1

Safety in Pregnancy

• Acyclovir is classified as FDA Category B in pregnancy, indicating that it is relatively safe for use during pregnancy. 1
• A registry of 596 infants exposed to acyclovir during first trimester showed no increased rate of birth defects compared to general population. 1

Severe Complications

• Women with significant varicella infection in pregnancy (e.g., pneumonitis) should be treated with oral antiviral agents. 4
• In cases of progression to varicella pneumonitis, maternal admission to hospital should be seriously considered. 4
• Intravenous acyclovir can be considered for severe complications in pregnancy (oral forms have poor bioavailability); the dose is usually 10 to 15 mg/kg IV every 8 hours for 5 to 10 days for varicella pneumonitis, and it should be started within 24 to 72 hours of the onset of rash. 4

Fetal and Neonatal Management

Fetal Monitoring

• Detailed ultrasound and appropriate follow-up is recommended for all women who develop varicella in pregnancy to screen for fetal consequences of infection. 4
• Women who develop varicella infection in pregnancy need to be made aware of the potential adverse maternal and fetal sequelae, the risk of transmission to the fetus, and the options available for prenatal diagnosis. 4

Peripartum Risk Period

• The highest-risk period for neonatal varicella is from 5 days before delivery to 2 days after delivery; historically, mortality without intervention is approximately 31%. 1
• All neonates born to mothers whose rash onset occurs within this window should receive VZIG, regardless of whether the mother received VZIG. 1, 2
• Neonatal health care providers should be informed of peripartum varicella exposure in order to optimize early neonatal care with VZIG and immunization. 4

Special Considerations for Premature Infants

• Very premature infants (<28 weeks gestation or <1,000 g) should receive VZIG after any postnatal varicella exposure, independent of maternal immunity status. 1
• Moderately premature infants (≥28 weeks gestation) should receive VZIG only if the mother lacks documented immunity. 1
• Healthy full-term infants exposed postnatally do not require VZIG, even if the mother has no prior varicella history. 1

Critical Pitfalls to Avoid

• Do not delay obtaining serology or administering VZIG: The 96-hour window is critical for maximal benefit, although some protection may persist if given up to 10 days after exposure. 1
• Do not withhold neonatal VZIG even when the mother has already received VZIG, if maternal rash occurs within the 5-day pre- to 2-day post-delivery window. 1
• Do not assume VZIG prevents infection: Approximately 60% of exposed neonates may still develop varicella, although disease severity and mortality are markedly reduced. 1
• Do not delay acyclovir treatment: Acyclovir treatment is most effective when initiated within 24 hours of rash onset. 1

Inadvertent Vaccination During Pregnancy

• Inadvertent administration of the live-attenuated varicella vaccine to a pregnant woman does not require pregnancy termination and has not been associated with congenital varicella syndrome in a 10-year prospective pregnancy registry. 1
• In a cohort of 131 live-born infants whose mothers were seronegative and received the vaccine during pregnancy (including 82 in the first or second trimester), no cases of congenital varicella syndrome were identified. 1
• Counseling for pregnant women who received the vaccine should focus on reassurance, as the data strongly support a low fetal risk profile. 1