Prenatal diagnosis of congenital parvovirus B19 infection: value of serological and PCR techniques in maternal and fetal serum.

Intrauterine infection with parvovirus B19 (B19) is associated with non-immune hydrops fetalis, miscarriage and stillbirth. Accurate laboratory tests for diagnosis of B19 infection are required to exclude other diagnoses. We analysed the diagnostic value of B19 IgM antibody testing and polymerase chain reaction (PCR) in the sera from 57 patients and their fetuses with abnormal ultrasonography. Viral DNA was found in 16 of the 58 fetuses (one twin pregnancy) whereas only 7 of these were tested positive for B19 IgM antibodies. The sera of all 16 mothers were also positive for B19 DNA. False-positive B19 IgM results were obtained from two fetuses. The study highlights the limitations of B19 IgM serology and shows for the first time that, if a sensitive PCR assay is used, DNA measurement is the best indicator of infection not only in the fetal blood but also in the maternal blood. This improves the diagnostic value of the laboratory results considerably. DNA assays are essential in cases of doubtful serological results.