Chapter 4 Parvovirus B 19 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 infection. Design: Study of the natural course of maternal parvovirus B19 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 parvovirus B19 viral DNA load and specific IgM and IgG antibodies in maternal serum. Results: Peak viral load levels occurred within one week after maternal infection and peak IgM levels were observed one week after the peak viral load levels. Approximation of IgG and IgM ratios usually took place 4 weeks after infection. Vertical transmission occurred 1 to 3 weeks after maternal infection, suggesting that fetal infection occurs during the maternal peak viral load. Conclusions: Maternal parvovirus B19 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 parvovirus B19 infection.