Background: Intrauterine parvovirus B19 (B19V) infection can be asymptomatic or may cause severe fetal complications. Information on serological and virological findings of infection in the fetus is scarce.
Methods: We determined B19V-DNA and anti-B19V antibodies in maternal and fetal blood samples obtained from 41 pregnancies that were complicated by prenatal B19V infection. Most fetuses presented with moderate to severe anemia or hydrops.
Results: At the time of fetal blood sampling, all mothers were B19V-DNA positive and B19V-IgG positive. B19V-IgM was detected in 95% of maternal blood samples. B19V-DNA, B19V-IgM, and B19V-IgG were detected in 100%, 28%, and 24% of fetal blood samples, respectively. The probability of a positive B19V-IgG or B19V-IgM finding in fetal blood increased with gestational age. B19V-IgG levels in maternal blood did not correlate with the likelihood of a positive B19V-IgG test in the fetus. The presence of B19V-IgG in fetal blood was accompanied by lower B19V-DNA levels and less severe clinical findings.
Conclusions: The lack of B19V-IgG in fetuses with B19V-derived anemia or hydrops is most likely due to a limited materno-fetal transfer of IgG and a poor fetal antibody response. Fetal B19V infection is poorly controlled in the absence of specific antibodies.