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I’m pregnant and have been exposed to Fifth disease; will it harm my baby?
Q: I'm in my 16th week of pregnancy, but at the end of 13 weeks, we found out my 2-year-old niece had Fifth disease. I had a blood test done and tested positive. What kind of risk does this pose for the baby? When are you considered contagious, and what are the symptoms?
Griselda Wilmington
A: Griselda, pregnant women are often exposed to children with Fifth disease, and in most cases the baby is born healthy. But it’s important that you be informed about Fifth disease and work closely with your obstetrician to follow your baby’s health.

Fifth disease is an infectious disease caused by human parvovirus B19. It is also known as Erythema infectiosum and “slapped cheek disease” because it causes a distinctive rash—very red cheeks and a splotchy red rash over the body that can come and go for weeks. It can also cause joint pain in adults. Fifth disease is actually contagious in the week before the rash appears when the child might have a runny nose, headache and fever.

When a pregnant woman is exposed to parvovirus, it usually doesn't cause harm; but it can infect the fetus and very rarely cause fetal anemia (low blood count), fetal hydrops (swelling), or miscarriage.

Your obstetrician can do some tests to help monitor your baby's health. It's good that you had a blood test done—this tests for antibodies that indicate exposure to parvovirus. It checks for two different antibodies, IgG and IgM, and meaning of the test depends on which antibodies are found to be positive and negative:
  • If you tested positive for the IgG antibody, it means you had the virus earlier (for example, when you were a child) and you're now immune to it, so you and your fetus are protected from getting infected again.

  • If you tested positive for the IgM antibody, it means that you were exposed for the first time recently, you're not yet immune to it, and your baby could be affected.

  • If you tested negative for IgG and IgM, it means that you don't show any sign of parvovirus infection in the past or recently; but your doctor might want to repeat the antibody test in two or more weeks to recheck for IgM to see if a recent infection might have occurred.

Be sure to clarify with your obstetrician which antibodies you tested positive for. If you tested positive for the IgM antibodies, your doctor may do ultrasounds or other tests to follow your baby's health. But try to relax and trust that it's most likely your baby is okay.
Karen Sokal-Gutierrez M.D., M.P.H. Pediatrician