Pregnancy and Chickenpox

Complications of Varicella Infection in Non-immune Pregnant Women

Jan 14, 2009 Stephen Allen Christensen

Exposure to chickenpox during pregnancy can cause serious problems for infants of non-immune mothers. Serologic tests for immunity can allay many fears.

Varicella-zoster virus (VZV) is a herpesvirus that causes chickenpox and shingles.

Chickenpox (varicella) is a highly infectious disease that is transmitted by respiratory droplets and causes a characteristic syndrome of fever, malaise and rash.

Shingles (zoster) simply represents a localized re-eruption of VZV, which lays dormant in the central nervous system of all individuals who get chickenpox.

VZV infection in a non-immune pregnant woman confers risks to the developing fetus and newborn. For a pregnant woman who already has antibodies to VZV (due to prior infection or immunization), exposure to chickenpox or shingles poses no risk to her infant.

Many individuals believe that they have never had chickenpox and are concerned about getting exposed to chickenpox or shingles. Before widespread varicella immunization programs were instituted, about 80% of women who could not recall having had chickenpox were, indeed, immune by serologic testing. (Brazin S, Simkovich J, Johnson, W. Herpes zoster during pregnancy. Obstet Gynecol 1979;53:175-81)

Immune women possess circulating antibodies that will protect their fetuses if they are exposed to VZV during their pregnancy. Even if a woman gets shingles during her pregnancy, she will not transmit the virus to her baby. She developed antibodies to VZV when she originally had chickenpox, and those antibodies have already crossed the placenta to protect the baby.

When a non-immune woman is exposed to VZV during pregnancy, the risk to the fetus depends on the gestational age of the fetus. Additionally, development of chickenpox in a pregnant woman may confer significant maternal risks; up to 30% develop varicella pneumonia, which may be more severe in pregnant women. (Perinatal viral and parasitic infections. ACOG Technical Bulletin Number 177—February 1993. Int J Gynaecol Obstet 1993;42:300-7)

Risks of Fetal Exposure to Varicella-Zoster Virus (VZV)

Congenital varicella syndrome

Usually associated with infection occurring in first 20 weeks of pregnancy

Risk is less than 2%

Effects on infant include:

• Limb hypoplasia (underdeveloped limbs)
• Cutaneous scarring
• Chorioretinitis (inflammation of the retina and pigment layers of the eye)
• Microphthalmia (underdeveloped eyes and orbits)
• Horner’s syndrome (damage to the sympathetic nerves innervating the eye)
• Cataracts
• Cortical atrophy (shrinkage of brain tissue)
• Mental retardation
• Microcephaly (abnormally small skull)
• Low birth weight

Neonatal Infection

If a pregnant woman develops chickenpox from five days before to two days after delivery, her infant is at substantial risk (approximately 50%) for neonatal varicella. Because the baby has been exposed to VZV but has no antibodies of its own, neonatal varicella is typically a severe infection that manifests with skin lesions and pneumonia; mortality approaches 30%.

Women who develop chickenpox prior to five days before delivery will transfer protective antibodies across the placenta to their infants, and there is essentially no risk of neonatal varicella.

Management of Exposure to Chickenpox or Shingles During Pregnancy

Uncertainties surrounding the varicella vaccine’s effectiveness and people’s uncertainty about their immune status have prompted many obstetricians to obtain varicella serologies for all their prenatal patients.

For pregnant women who experience exposure to VZV—and who don’t know their immune status—management is relatively straightforward:

• If serology cannot be obtained within 96 hours of exposure, or if serology reveals inadequate immunity, the woman is given varicella-zoster immune globulin (VZIG).
• If a woman develops chickenpox in spite of VZIG, she is treated with acyclovir, an antiviral agent. Infected women then undergo regular ultrasounds—and possibly cordocentesis—to evaluate for congenital varicella syndrome.
• For infants whose mothers develop perinatal varicella infections, VZIG is administered upon delivery, and the newborns are isolated.
• Immunization is not given during pregnancy, as it is a live-virus vaccine.

(Adapted from Ely J, et al. Evaluation of pregnant women exposed to respiratory viruses. Am Fam Phys 2000;61(10):3065-74)

The copyright of the article Pregnancy and Chickenpox in Pregnancy & Childbirth is owned by Stephen Allen Christensen. Permission to republish Pregnancy and Chickenpox in print or online must be granted by the author in writing.

Fetal Ultrasound

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