Parvovirus B19 infection in pregnancy: maternal and fetal viral load measurements related to clinical parameters.

Objective: To correlate quantitative maternal and fetal parvovirus B19 (B19V) viral loads and antibody levels at intrauterine transfusion (IUT) as a predictor of fetal morbidity.
Methods: Prospectively collected clinical data and quantitative B19V viral load and specific IgM and IgG values in fetal and maternal blood samples taken during IUT.
Results: Maternal IgM and IgG levels exceeded fetal antibody levels. Fetal viral load measurements correlated positively with maternal viral loads and exceeded maternal viral load 10(5)-fold (p < 0.0001). Maternal B19V IgM and fetal B19V viral load showed a positive correlation (r = 0.840, p = 0.007). No relation was found between fetal viral load and severity of fetal anemia derived from Doppler flow measurements in the middle cerebral artery.
Conclusions: Maternal and fetal B19V viral load values are highly interrelated, suggesting continuous maternal and fetal viral replication or a fetal source of maternal viremia. Maternal B19V IgM values may predict the severity of fetal infection, but the severity of B19V induced fetal anemia cannot be predicted using fetal or maternal viral loads. Fetal ultrasound remains the gold standard for identifying fetal anemia in B19V infection.
(Copyright 2007 John Wiley & Sons, Ltd.)