ABSTRACT
COMPLICATIONS Of the infected fetuses, about 5% to 20% can develop anemia, of which 30% to 50% develop hydrops fetalis (about 2%–6% of all infected fetuses) with some series showing hydrops rates as high as 66% of anemic fetuses [5] (Figure 49.2). Overall, the data suggest a rate of 1% to 4% for fetal hydrops in infected mothers [3] with rates as high as 8%–10% with infections occurring between 9 and 20 weeks [6]. The risk of fetal death is 1% to 6% of all infected fetuses [7]. Fetal death occurs almost exclusively in hydropic cases diagnosed at <20 weeks [8], especially if cases >20 weeks are treated with timely transfusion (90% survival) [7]. Early embryonic/ fetal death may manifest as miscarriage. A recent casecontrol study demonstrated an increased association of first trimester miscarriage with positive Parvovirus IgM women (OR 1.71, 95% CI 1.02-2.86) [9]. Overall for infected mothers <20 weeks, there is an approximate 10% risk for fetal loss. Although acute parvovirus infection may occur relatively commonly during pregnancy, an adverse fetal outcome is an uncommon complication [4,10,11]. Rarely, parvovirus has been detected in fetuses with hydrocephalus (possibly from vasculitis), but it is unclear if malformations seen with parvovirus are just coincidental and not related to the viral infection. Parvovirus B19 may be an important cause of fetal death not always associated with fetal hydrops. All cases of fetal death, especially those associated with hydrops, should be considered for testing for parvovirus B19 by polymerase chain reaction (PCR). Maternal serology might be a less sensitive determinant for parvovirus B19-associated fetal death because immunoglobulin M (IgM) response generally lasts for two to four months, and parvovirus B19 infection can already be persistent in fetuses during the early stages of pregnancy, eventually leading to fetal death months later (see also Chapter 54). The more mature immune response in older fetuses could delay any pathogenic consequences of parvovirus B19 infection, resulting in a lower rate of hydrops than in younger fetuses [12,13].
