Chicken Pox and the Pregnant Woman

mother holding her daughter who has chickenpox
What do you need to know about chickenpox during pregnancy?. Photo©monkeybusinessimages

What do you need to know if you are exposed to or develop chicken pox during pregnancy? How might chicken pox affect your baby and how may it affect your own health? Is there anything you can do to prevent chicken pox in yourself or your baby?

Chicken Pox in Pregnancy

Chicken pox is usually a benign, self-limited, viral infection caused by the varicella virus. However, chicken pox acquired during pregnancy causes an increased risk of complications for the mother and the infant.

The time of infection, whether during early pregnancy or near delivery, plays a significant role in the risk to the mother and child.

Pregnant Women Exposed to Chicken Pox

Pregnant women who have a history of a previous chicken pox infection or who have been immunized have antibodies to the virus. These antibodies are transferred to the infant through the placenta throughout the pregnancy. Therefore, pregnant women who are immune and are exposed to someone with chicken pox do not need to worry about complications for themselves or their infant.

In contrast, women who are susceptible to chicken pox (either through never having the infection or not having been immunized) are at risk. If you believe you have been exposed to chicken pox while pregnant call your doctor right away.

In addition, women who are not immune to varicella, but are exposed may be treated with varicella-zoster immunoglobulin (VZIG), a substance that triggers an immune response against the varicella virus.

Testing for Immunity in Pregnancy

All women should be questioned about previous chicken pox infection or immunization at their first prenatal visit. Of those women who do not remember a past infection or immunization, 80 to 90 percent have antibodies and are considered immune. For this reason, testing for antibodies against chicken pox as evidence of immunity is controversial, but many practitioners obtain this test at the first prenatal visit.

Vaccination against chicken pox during pregnancy is not recommended.

The chicken pox vaccine is a "live virus" vaccine and carries the theoretical risk of causing an infection, especially in those who are immunosuppressed or pregnant.

Maternal Complications of Chicken Pox in Pregnancy

A primary chicken pox infection occurs in only 0.05 to 0.07 percent of pregnancies because most women of childbearing age have immunity to the varicella virus (because of a previous infection or immunization.) Women who do acquire chicken pox while pregnant, especially in the third trimester, are at a greater risk of developing varicella pneumonia. Varicella pneumonia is a potentially life-threatening infection of the lungs by the varicella virus.

Infant Complications of Chicken Pox in Early Pregnancy

Primary chicken pox infection in the first trimester of pregnancy, especially weeks 8 to 12, carries a 2.2 percent risk of congenital varicella syndrome. Manifestations of congenital varicella syndrome in a child include:

  • Scarring of the skin
  • Microcephaly (a smaller than normal head)
  • Eye problems
  • Low birth weight
  • Mental retardation

Infant Complications of Shingles in Pregnancy

Shingles is a condition caused by the re-activation of the chicken pox virus at any time following the original infection. After a primary chicken pox infection clears, the virus remains dormant and may reactivate, especially when the body is immunosuppressed. While we don't hear as much about the potential impact of shingles on pregnancy, a 2016 study found that of 130 women who delivered infants with congenital varicella syndrome, 2 of the cases were related to shingles rather than primary chicken pox infections. Recognizing the early signs and symptoms of shingles is important for everyone, especially pregnant women, as treatment can greatly reduce the severity of the disease, but only when started during the first few days of the illness.

Infant Complications of Chicken Pox in Late Pregnancy

If a woman acquires a primary chicken pox infection anytime in the period which spans 5 days before and 2 days after delivery, her newborn is at risk for disseminated varicella infection. Disseminated varicella infection occurs when the virus infects a newborn before the transfer of protective maternal antibodies. This overwhelming viral infection led to death in roughly 30 percent of children who developed the disseminated disease, but the mortality rate has decreased to 7 percent with the use of varicella-zoster immune globulin.

Treatment of Pregnant Women With Chicken Pox

Women who acquire primary chicken pox during pregnancy should be treated with the antiviral drug Zovirax (acyclovir,) a medication which appears to have a good safety profile in pregnancy. Pregnant women with varicella pneumonia should be treated with intravenous acyclovir and be observed in the hospital.

Treatment of Infants With Chicken Pox

Infants whose mothers develop varicella 5 days before delivery or 2 days following delivery should receive varicella-zoster immunoglobulin (VZIG) after birth.

Infants who develop varicella during the first 2 weeks of life should be treated with intravenous acyclovir.

Postpartum Vaccination

All women who are found to be non-immune to chickenpox during pregnancy, and do not develop the disease during pregnancy, should be immunized in the postpartum period to prevent the risk in later pregnancies.

Bottom Line

It can be very frightening if you develop or are even exposed to chickenpox during pregnancy. You may have heard stories about how chickenpox can affect unborn children or children shortly after birth. Fortunately, there are many things that can be done to reduce the risk of chickenpox both for yourself and your baby, or to treat the infection should it occur.

Those who are planning pregnancy should find out if they had chickenpox as well as whether they have had the vaccine. If immune status is unknown, a blood test to check immunity can be done and the vaccine given if needed. If you are planning on being immunized, it is recommended that you do so 3 months or more before becoming pregnant.

If you are pregnant and uncertain about your immunity to chickenpox, talk to your obstetrician. You may have been tested at your first prenatal visit. If you have been exposed to the virus, call your doctor immediately. Preventative measures are most effective when employed as soon as possible after exposure and long before any symptoms develop.

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