Chickenpox (Varicella Zoster)
- Introduction
- Fetal exposure to Varicella Zoster Virus
- Infant of a mother with perinatal chickenpox
- Postnatal exposure to VZV (up to 28 days)
Introduction
The Varicella-zoster virus is a herpes virus causing chickenpox as the primary infection or herpes zoster after reactivation from its latent form in dorsal root ganglia.
Fetal exposure to Varicella Zoster Virus
- Fetal varicella due to primary infection with chickenpox in pregnancy is usually benign
- Congenital varicella syndrome (CVS) is thought to result from in utero viral reactivation or disseminated zoster infection
Risk is higher when maternal chickenpox occurs before 20 weeks and is estimated at approximately 2%.
CVS is associated with
Management
- give ZIG (6mL IMI) within 72 hours of significant exposure to the pregnant woman if sero-negative or if there is a negative history and sero-testing is unavailable
- continue monitoring, including with ultrasound, since ZIG reduces the clinical attack rate in the pregnant woman but may not eliminate fetal risk
- negative amniotic fluid PCR correlates well with a good outcome but positive PCR correlates poorly with congenital varicella syndrome development
Areas of Uncertainty in Practice
- termination of pregnancy would not usually be offered but may require discussion
Infant of a mother with perinatal chickenpox
When maternal chickenpox develops within 7 days and up to 28 days after delivery the newborn is at risk of developing severe neonatal varicella (reported mortality rates of up to 30%) since the newborn will not have any passive immunity.
Management
- give the infant ZIG (2mL IMI) as soon as possible after delivery or onset of maternal illness. ZIG must be given within 72 hours
- while in hospital, a mother and/or infant with lesions should be isolated from other patients. A mother with lesions does not need to be isolated from her own infant
- continue to encourage breastfeeding unless lesions are on or near the nipple
- admit infant into hospital isolation room if rash develops
- give IV aciclovir (20mg/kg every 8hours) to infants who develop chickenpox and
- did not receive ZIG prophylaxis within 24 hours
- are immunocompromised
- are premature (less than 28weeks gestation at birth)
Areas of Uncertainty in Practice
- The high risk period for severe infection varies between authorities. These conservative recommendations follow the published Australian guidelines
Postnatal exposure to VZV (up to 28 days)
Chickenpox is a common childhood illness so the commonest situation is of a sibling developing chickenpox. The risk to the infant relates to whether transplacental transfer of maternal antibody has occurred.
Significant exposure includes face to face contact for more than 5 minutes, or contact for more than an hour with a person who has uncrusted lesions or develops them within the next 48 hours.
Management
- give ZIG (2mL IMI) immediately if
- mother is seronegative
- her sero-status cannot be determined and history is negative
- infant born at less than 28weeks gestation or <1000gm birthweight</li/>
- encourage normal care. Do not exclude infant from family contact
- admit for aciclovir treatment if infant becomes unwell
References
The Management of varicella-zoster virus exposure and infection in pregnancy and the newborn period A. Heuchan, D. Isaacs on behalf of the Australasian Subgroup in Pediatric Infectious Diseases of the Australasian Society for Infectious Diseases MJA 174 2001 288-291
Please remember to read the disclaimer.
We welcome your Feedback.