Parvovirus B19 infection in pregnancy studied by maternal viral load and immune responses.

OBJECTIVES

Facilitate risk assessment of vital complications in fetuses of pregnancies affected by acute parvovirus B19 (B19V) infection.

DESIGN

Study of the natural course of maternal B19V infection in four cases, from early pregnancy on.

SETTING

University Medical Center in the Netherlands.

POPULATION: Pregnant mothers attending obstetric services.

METHODS

Serial measurements of the maternal and fetal or neonatal viral load and antibody responses.

MAIN OUTCOME MEASURES: Maternal and fetal/neonatal serum B19V viral DNA load and specific IgM and IgG antibodies in maternal serum.

RESULTS

Peak viral load levels occurred within 1 week after maternal infection and peak IgM levels were observed 1 week after the peak viral load levels. Approximation of IgG and IgM ratios usually took place 4 weeks after infection. Vertical transmission occurred 1-3 weeks after maternal infection, suggesting that fetal infection occurs during the maternal peak viral load.

CONCLUSIONS

Maternal B19V DNA load levels and IgM responses are useful to estimate the risk of parvovirus B19-associated fetal complications. The maternal peak viral load directly precedes the onset of fetal infection and may be used to indicate the stage of intrauterine B19V infection.