Objective.To clarify the relation between the time of parvovirus B19 (B19) infection in pregnancy and fetal outcome, including the viral persistence in the fetus.Methods.Among 57 pairs showing serologic and/or virologic evidence of maternal and fetal B19 infection between 1986 and 1999 in Japan, 13 maternal-fetal pairs with the time of maternal B19 infection documented were retrospectively evaluated for fetal outcome and viral persistence.Results.Nonimmune hydrops occurred at 23, 21 and 26 gestational weeks (gw) in three fetuses as a result of their mothers’ symptomatic infection (erythema infectiosum) at 3, 16 and 19 gw, respectively. Spontaneous abortion without hydrops and intrauterine growth retardation resulting in small-for-gestational age (SGA) classification occurred in two fetuses whose mothers had developed erythema infectiosum at 5 and 16 gw, respectively. Eight fetuses were asymptomatic as a result of their mothers’ infection at 6, 9, 12, 15, 18, 23, 23 and 33 gw, respectively. B19 DNA was detected in neonatal serum in all nine cases tested.Conclusion.Maternal B19 infection throughout gestation including the early stage after fertilization caused fetal infection that persisted until intrauterine fetal death with or without nonimmune hydrops or until the neonatal period after birth.