Varicella Zoster Virus Infection During Pregnancy

Lev D. Kandinov, MD

Disclosures

March 03, 2005

Question

I have an antenatal mother in her 75th day since her last menstrual period with confirmed pregnancy test. She also is manifesting classic herpes zoster infection in the left intercostal zone. What are the effects of the infection on the fetus? What is the appropriate course for managing the infection?

A. Victor Jerome, DCH

Response from Lev D. Kandinov, MD

Varicella zoster virus (VZV) is a DNA virus and a member of the herpesvirus family. It is highly infectious and is transmitted by direct contact and through respiratory droplets. About 90% of infections are contracted in the first decade of life, and immunity to VZV is lifelong. Morbidity and mortality are much higher among older persons who are newly exposed to VZV.

All women of reproductive age should be screened for immunity to VZV. Women who did not have childhood "chickenpox" (or do not recall having had it) should be tested for serum VZV immunoglobulin (Ig)G. Women of reproductive age who are not immune should be offered varicella vaccine. Note, however, that this vaccine is contraindicated during pregnancy. Therefore, pregnant women who are not immune to varicella should be educated to avoid exposure to persons who have varicella or herpes zoster. Nonimmune pregnant women who have been exposed to varicella should be offered varicella-zoster immune globulin (VZIG), preferably within 72-96 hours post exposure. Prophylactic acyclovir, 800 mg orally 5 times daily for 5-7 days, is also effective in preventing the infection.[1,2] Pregnant women who have been exposed and are not immune should be counseled about the clinical manifestations of varicella that they may experience, especially pneumonia and encephalitis.

Reactivation of latent VZV results in herpes zoster infection. This infection is less serious than varicella secondary to the presence of maternal antibodies; however, it can be very serious in immunocompromised patients. The infection manifests clinically as fever, malaise, and skin rash. The rash is painful and is usually confined to a dermatome. Serious life-threatening complications of the infection include pneumonia (up to 20% of pregnant patients) and encephalitis (up to 1% of pregnant patients).

Pregnant women with herpes zoster symptoms should be treated with oral acyclovir, unless hospital admission is warranted. Oral antiviral agents (acyclovir, valacyclovir, or famciclovir) have been shown to significantly reduce herpes-related symptoms as well as the duration, intensity, and prevalence of zoster-associated pain.[3] According to Drugs in Pregnancy and Lactation, Sixth Edition ,[4] famciclovir, a category C drug, has not been studied enough in pregnant women. Valacyclovir, also a category C drug, is metabolized to acyclovir. Acyclovir is the drug of the 3 that has been most extensively studied in pregnant women and is the agent most commonly used to treat patients with VZV during pregnancy. All HIV and immunocompromised women who are pregnant and are manifesting VZV infection should be admitted to the hospital for intravenous acyclovir.[1]

A pregnant woman who has been exposed to VZV before pregnancy should be reassured that her fetus is safe. It is well documented in the literature that IgG antibodies are transplacentally passed to the fetus providing the necessary immunity. These antibodies persist in the newborns for up to 6 months of life.[5] A pregnant woman manifesting VZV infection should be counseled about the risk of viral transmission to the fetus and the risks of fetal anomalies. They should also be informed that these risks are very low. The incidence of fetal anomalies after an early exposure (before 20 weeks) is 1.2% to 2.0%.[2,6,7] VZV infection of the fetus occurs primarily via hematogenous dissemination across the placenta. This infection may lead to spontaneous abortion, fetal demise, and varicella embryopathy (eg, limb hypoplasia, microcephaly, muscle atrophy, cataracts, and mental retardation). Prenatal ultrasound and magnetic resonance imaging have been used to document the extent of tissue damage in fetal varicella syndrome.[8] Findings include oligohydramnious, intrauterine growth restriction, hydrops, limb deformities, and microcephaly.

Neonatal infection may occur in 10% to 20% of neonates whose mothers became acutely infected from 5 days before delivery to 2 days after the delivery. It results from hematogenous dissemination of the virus across the placenta in the absence of maternal antibodies. Infants become symptomatic 5-10 days postpartum. The clinical picture may vary form skin lesions to systemic illness, pneumonia, for example.

In acutely infected mothers the delivery should be postponed 5-7 days to prevent the spread of VZV to the neonate. If this is not possible, the neonate should be given VZIG immediately after birth and should be isolated from the mother if the latter has skin lesions/rash present.[1]

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