Parvovirus B19 in pregnancy.

Parvovirus B19 is a widespread infection that may affects 1-5% of pregnant women, mainly with normal pregnancy outcome. The prevalence of infection is higher during epidemics - between 3 and 20% with sero-conversion rate of 3-34%. Infection during pregnancy can cause a variety of other signs of fetal damage. The risk of adverse fetal outcome is increased if maternal infection occurs during the first two trimesters of pregnancy but may also happen during the third trimester. It is a significant cause of fetal loss throughout pregnancy, but has a higher impact in the second half of pregnancy when spontaneous fetal loss from other causes is relatively rare. Parvovirus infection can cause severe fetal anemia as a result of fetal erythroid progenitor cells infection with shortened half life of erythrocytes, causing high output cardiac failure and therefore nonimmune hydrops fetalis (NIHF). The P antigen expressed on fetal cardiac myocytes enables the Parvovirus B19 to infect myocardial cells and produce myocarditis that aggravates the cardiac failure. Although there are several reports of major congenital anomalies among offspring of mothers infected by Parvovirus, the virus does not seem to be a significant teratogen. Since Parvovirus B19 infection can cause severe morbidity and mortality, it should be part of the routine work up of complicated pregnancies. Risk assessment for maternal infection during pregnancy is especially important during epidemics when sero-conversion rates are high.