Slapped Face Syndrome is caused by a virus called parvovirus B19 that blocks red blood cell development and causes a rash on the face. The parvovirus B19 is to blame for the reaction. Women who are pregnant are susceptible to parvovirus B19 in 50% of cases, but few contract it or develop Slapped Face Syndrome. When a pregnant woman does come down with the virus, researchers have found an increased risk of fetal spread and possibly fetal death.

In about 30% of the Slapped Face Syndrome cases, women pass the virus onto the fetus. In 5% to 10% of those cases the fetus will be lost due to the virus. While the adult immune system can fight off the virus, in most cases, the fetus will often suffer long term side effects. These side effects can include hepatitis, anemia, inflammation of the heart and cardiac failure or death.

The risk to the fetus is determined by gestational age. If a pregnant woman contracts the virus in the first trimester and passes it to the fetus, the rate of death could be as high as 19%. Between 13 and 20 weeks, that rate drops to 15%. After week 20 of gestation, fetuses have a 6% increased risk of death from the parvovirus B19.

There is no vaccine or therapy for parvovirus B19 so doctors need to be familiar with the symptoms and potential risk of fetal infection. The study was published in BJOG: An International Journal of Obstetrics and Gynaecology.

Source: Lamont R, Sobel J, Vaisbuch E, Kusanovic J, Mazaki-Tovi S, Kim S, Uldbjerg N, Romero R. Parvovirus B19 infection in human pregnancy. BJOG. October 2010.

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