Dangers of parvovirus during pregnancy

Fifth Disease, also known as human parvovirus B19, is a common, viral illness that typically spreads during outbreaks among children in elementary and middle school in late winter and early spring. Although it generally causes only a mild illness that resolves on its own, it can cause complications for children with blood disorders or a weakened immune system. It can also be serious if it is contracted by pregnant women, since the virus can cross the placenta.

Why is it so dangerous? 

Although Fifth Disease is highly contagious, it is usually a mild illness. Symptoms typically include:

  • mild fever
  • sore throat
  • flu-like symptoms
  • bright red rash on the face, like “slapped cheeks”
  • lacy, slightly raised rash all over the body

Some people with the virus have no symptoms. In fact, according to the Centers for Disease Control and Prevention (CDC), about half of all adults have had the virus in their lifetime and developed immunity to it.

Many pregnant women who become infected with Fifth Disease will deliver healthy babies. But about one-third of the time, the virus crosses the placenta. When this happens, the unborn baby may be infected and go on to have serious complications, including anemia, heart inflammation, or fetal hydrops (abnormal accumulation of fluid). Some studies suggest severe and irreversible neurological symptoms may occur in babies who survive in-utero infection.

About 1 in 10 fetal parvovirus infections result in miscarriage or stillbirth. The risk is highest for infections that occur during the first 20 weeks of pregnancy. 

Some experts suggest that tests for parvovirus B19 immunity should be included as part of a woman’s routine prenatal bloodwork, so that they can be aware of their risk—especially if there is a young child in the family. A mother who hasn’t developed immunity to the virus and whose child is infected by it has an estimated 50–90 percent of catching it. By comparison, a child in day care has only a 20–30 percent chance of catching it from a sick peer.

What treatment is available to pregnant women? 

Treatment for parvovirus tends to focus on relieving symptoms of fever, joint pain, fatigue, and itching—especially for women in the first trimester of pregnancy, whose unborn infants are too small for any available treatment. (Immunoglobulin treatment may help, but it is currently in the research phase.) 

For women who are in the second or third trimester of pregnancy when they are infected with parvovirus B19, treatment usually involves: 

  • Frequent (weekly) ultrasounds to monitor fetal health. 
  • If severe anemia or hydrops develops, and it is the third trimester, the baby may be delivered. This is only done when the risks of an early delivery are felt to be less than the risks of continued pregnancy.
  • If severe anemia or hydrops develops, and the baby cannot be delivered yet, fetal blood transfusions may be considered. Transfusion isn’t without risks; various studies estimate that risk of death in utero may still be 10 to 30 percent of infected fetuses. However, in serious cases, this risk may be lower than what the baby faces without treatment.

Fortunately, many pregnant women who contract parvovirus B19 will not have the virus pass to their babies. Even when it does, many of the babies will be born healthy. Parvovirus does sometimes resolve on its own, even for babies in utero. 

Last updated June 20, 2021

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