The incidence of, and factors leading to, parvovirus B19-related hydrops fetalis following maternal infection; Report of 10 cases and meta-analysis

Objectives: to clarify the approximation of the frequency of B19-related nonimmune hydrops fetalis (NIHF), and to know the critical period during which maternal infection led to NIHF. Methods: we investigated the characteristics of 10 cases of antenatal B19 infection diagnosed over the past 10 gears in Miyagi prefecture, Japan, and performed a meta-analysis of these cases and those previously reported in the literature. Results: NIHF caused by intrauterine B19 infection was diagnosed between 11 and 23 weeks of gestation in 10 women over the past 10 years in Miyagi prefecture, Japan. The source of infection was the mother's older child in six out of 10 cases, and children at a kindergarten where the mothers worked in two cases. The interval between the onset of infection and the diagnosis of NIHF ranged from 2 to 6 weeks. B19 infection was responsible for 10 (15.2%) in 66 cases of aetiology unknown NIHF in this study, and for 57 (19.1%) of 299 cases of non-malformed or aetiology-unknown NIHF by meta-analysis of the literature. Meta-analysis of the 165 reported cases of antenatal B19 infection, including the 10 cases described above, showed that there was a 10.2% excess risk of fetal death in women infected with B19 during pregnancy and a 12.4% excess risk in women infected during the first 20 weeks of pregnancy. Transplacental transmission was confirmed in 69 (24.1%) of 286 cases. The mean gestational age at diagnosis of NIHF was 22.8 ± 5.1 weeks. The mean interval between the onset of maternal infection and diagnosis of NIHF was 6.2 ± 3.7 weeks. Conclusions: these approximations will be useful for counselling and management for pregnant women. The critical period during which maternal infection led to NIHF correlated with the hepatic period of hematopoietic activity. These findings suggest that parvovirus B19 may have an affinity for erythroid lineage cells at the hepatic stage of hematopoiesis, which may strongly influence the clinical features of feto-maternal B19 infection.