Varicella-zoster virus (VZV) is a member of the herpesvirus family. Primary maternal VZV infection (chickenpox) can result in fetal or neonatal infection; however, reactivation infection (zoster) does not result in fetal infection. Primary maternal VZV infection during the last trimester can cause pneumonia with significant morbidity and mortality. Three forms of varicella-zoster infections involve the neonate: fetal, congenital, and postnatal.
Definition. This form occurs when the mother has her first exposure to VZV during the first half of pregnancy.
Incidence. This form is fortunately rare; the incidence of varicella during pregnancy is estimated at 1.6–4.6 per 1000. The incidence of embryopathy and fetopathy after maternal varicella infection in the first 20 weeks is ~1% . Recent evidence suggests that the incidence is much lower than previously estimated.
Pathophysiology. Maternal transmission of the virus probably occurs via respiratory droplets or direct contact with chickenpox or zoster lesions. The virus replicates in the oropharynx, and viremia results, before the onset of rash, with transplacental passage to the fetus. Almost all cases reported have involved exposure between the 8th and 20th weeks of pregnancy. From the pattern of defects seen in the fetal varicella syndrome, particularly the scarring and limb hypoplasia, it has been suggested that fetal varicella syndrome is the result of intrauterine herpes zoster. The extremely short latent period between fetal infection and reactivation is the consequence of the lack of cell-mediated immunity in the fetus before 20 weeks' gestation. The defects probably result from viral replication and destruction of developing fetal ectodermal tissue.
Risk factors. A mother with her first exposure to VZV during the first half of pregnancy (usually exposure between the 8th and 20th week). One study found the risk was higher if the maternal rash onset was between 13 and 20 weeks of pregnancy.
Clinical presentation. Sauerbrei and Wutzler summarized the main symptoms of FVZS after studying 124 cases reported in the literature as the following:
Skin lesions (72%) involve cicatricial scars and skin loss.
Central nervous system defects or disease (62%): microcephaly, seizures, encephalitis, cortical atrophy and spinal cord atrophy, mental retardation, and cerebral calcifications.
Eye diseases (52%): microphthalmia, endo-ophthalmia, chorioretinitis, cataracts, optic atrophy, and Horner syndrome (ptosis, miosis, and enophthalmos).
Limb hypoplasia and other skeletal defects (44%).
Intrauterine growth restriction (35%).
Diagnosis. Alkalay et al proposed the following criteria for the diagnosis of FVZS in the newborn:
Appearance of maternal varicella during pregnancy.
Presence of congenital skin lesions in dermatomal distribution and/or neurologic defects, eye disease, or limb hypoplasia.
Proof of intrauterine VZV infection by detection of viral DNA in the infant by polymerase chain reaction (PCR); presence of VZV-specific immunoglobulin (Ig)M; persistence of VZV IgG beyond 7 months of age, or appearance of zoster during early infancy.
VZV DNA PCR (both from fetal blood or amniotic fluid) appears to be sensitive and accurate in detecting fetal infection; however, most of the "infected" fetuses are morphologically normal (ie, not affected by FVZS). Prenatal diagnosis is most often done ...
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