Fifth's Disease and Your Baby

Frederick R. Jelovsek, MD

Fifth disease, erythema infectiosum or slapped child disease, is a not infrequent childhood infectious disease in which children have fevers, tiredness and extensive red rashes of the cheeks and face. It is caused by parovirus B19 and spreads like chicken pox or measles in preschool and school age children.

Every once in awhile, an obstetrician diagnoses a baby who has died before birth with a condition in which there is massive fluid swelling (hydrops) of the fetus. In earlier times this was mostly due to Rh isosensitization in which the mother had an Rh negative blood type and the baby had an Rh positive blood type. In the last 20-30 years, treatment of Rh negative mothers with Rhogam has drastically reduced this immune hydrops occurance. Now the most frequent cause of hydrops is non-immune and is often caused by B19 parovirus infection in pregnant women.

Since B19 parvovirus infection in pregnancy has been associated with stillborn babies, the question becomes -- should pregnant women be excluded from the workplace when there is a epidemic of fifth disease? Another concern would be if any of your family was exposed while you were pregnant, how likely is it that your unborn child would be affected?

A recent article by Harger and others, Harger JH, Adler SP, Koch WC, Harger GF:Prospective evaluation of 618 pregnant women exposed to parovirus B19; Risks and symptoms. Obstet Gynecol 1998;91:413-20, looked at this risk. In their study almost 50% of the women who were concerned about a new exposure to fifth disease, had already been exposed at some previous time in their life so they were not at risk of getting infected again.

One in six (16.7%) of the 259 susceptible women got the disease but none of their unborn babies developed hydrops or died before birth. Women whose own child was infected also got infected more often (29%) but school teachers had an average infection rate (18%).

While this study does not mean there is no risk to the pregnant women, it appears the attack rate of the fetus is quite low and most pregnant women who are exposed can be reassured. It is still recommended that if exposure is suspected, blood tests are drawn for IgM and IgG antibodies to B19 parovirus and that an ultrasound is performed approximately 6-8 weeks after exposure and 14-16 weeks after exposure if the IgM indicates a current infection.