Exposure to fifth disease in pregnancy.

QUESTION: One of my pregnant patients came for a routine prenatal visit at 20 weeks' gestation. Near the end of the consultation, she asked me about "slapped cheek" disease and pregnancy, as her son had been diagnosed with fifth disease the previous week. What is the current guideline for pregnant women exposed to parvovirus B19?

ANSWER: The rate of vertical transmission during maternal parvovirus B19 infection is estimated at 33%, with fetal complications occurring in 3% of infected women. Fetal complications comprising hemolysis, anemia, and nonimmune hydrops fetalis and fetal loss are more frequent when maternal infection occurs before 20 weeks of gestation. The first step in the management of this patient would be to obtain immunoglobulin (Ig) M and IgG titres against parvovirus to evaluate if the patient has had previous immunity against the disease. If results are negative for IgG but positive for IgM (ie, primary infection), this patient would need close obstetrical monitoring for the following weeks, including serial ultrasounds to rule out fetal anemia and hydrops fetalis.