Chicken pox (varicella) is a highly contagious herpes virus that is transmitted by respiratory droplets. While the incidence of chicken pox has decreased dramatically in recent years thanks to the varicella vaccine, the virus is still risky to susceptible individuals. Young children, the elderly, immunocompromised patients, and pregnant women are most at risk of severe disease.
Pregnant women can contract chicken pox in two ways. They are most commonly exposed to the virus through someone who has the infection. Rarely, they can also contract chicken pox from coming into contact with someone who has shingles. Fortunately, most pregnant women have been exposed to varicella in their lifetime or have received the vaccine.
Exposure to chicken pox in pregnancy can be risky to the developing fetus, especially in the first trimester. Although only 2 percent of exposed fetuses actually develop congenital varicella, the effects on the fetus can be devastating. Complications can include arm and leg malformations, skin scarring, brain atrophy, small head, cataracts, and developmental delay. Pregnant women who have been exposed to chicken pox in the first trimester should undergo ultrasounds at 18 and 28 weeks of gestation, although the ultrasounds may not definitively detect congenital varicella.
Neonatal varicella is another disease process that can lead to devastating consequences in newborns. Pregnant mothers who are exposed to varicella between five days before and two days after delivery can transmit the infection to their infants up to 50 percent of the time. As a result, infants can develop severe pneumonia and skin complications. Neonatal varicella has a mortality rate of more than 30 percent. Fortunately, infants can be given a dose of varicella immunoglobulin to help prevent or lessen potential infection.
If a pregnant woman is exposed to chicken pox and she is not sure if she has ever had the disease, she should immediately have blood testing done to measure her serum antibodies to varicella. These blood tests will make sure she is immune to the virus. If this is not possible, or the results will take more than four days, she should receive varicella immunoglobulin to prevent or lessen maternal infection. Studies are unclear as to whether or not the varicella immunoglobulin prevents congenital varicella, but it will protect the mother against severe disease. If she develops a severe case of chicken pox, she should be started on Acyclovir.
Reviewed by Dr. Jen Lincoln, April 2020
- Pregnant women, young children, and the elderly are most at risk for chicken pox.
- The virus can be contracted either by being exposed to someone who has the infection or someone that has shingles.
- Developing fetuses that are exposed to varicella are at risk for devastating complications.