When is a pregnant woman at increased risk of neonatal VZV infection?

A pregnant woman is at increased risk of neonatal varicella-zoster virus (VZV) infection 5 days prior to delivery or 2 days postpartum due to the timing of maternal infections and the potential for transmitting the virus to the newborn. If a mother develops varicella (chickenpox) close to the time of delivery, especially within this window, the risk of neonatal infection is heightened because the infant has not had sufficient time to develop protective immunity through transplacental antibodies.

Transmission can occur when the mother is actively shedding the virus, which typically happens just before the onset of the rash and remains high until crusting of the lesions. If a maternal infection occurs during this critical period, the infant can be exposed to the virus during birth or shortly after, thereby increasing the risk of developing congenital varicella syndrome or other complications associated with neonatal infection.

In contrast, infections during other stages of pregnancy do not pose the same level of risk for the newborn, primarily because by the time the infant is born, maternal antibody transfer may provide some level of protection, especially if the infection occurs in the first or second trimester. Thus, timing in relation to delivery is crucial in assessing risk for VZV infection in neonates.