Prenatal parvovirus B19 infection

Abstract

Parvovirus B19 (B19V) causes erythema infectiosum, a.k.a., fifth disease. This disease primarily affects children. It is generally self-limiting and subsides after 1-2 weeks. In pregnancy, the virus can cross the placenta and result in a fetal infection. This may lead to severe fetal anemia, hydrops fetalis, a miscarriage, or intrauterine fetal death. The risk of long-term sequelae also appears to be increased. About one-third of pregnant women are not immune to B19V and, therefore, are at risk to contract a primary infection. The seroconversion rate during pregnancy is generally around 1-2%. During a primary infection, maternal-fetal transplacental transmission of B19V occurs in about 30-50% of the cases and the risk of fetal infection increases with advancing gestational age. The risk of severe fetal anemia or hydrops is around 3-4% overall and is around 6-7% if the primary infection occurs before 20 weeks' gestation. Fetal monitoring in women with a primary B19V infection includes regular ultrasound examinations looking for evidence of hydrops fetalis and Doppler measurements of the middle cerebral artery peak velocity. Fetal blood sampling is performed if a significant anemia is suspected and, if such is found, an intrauterine blood transfusion is needed. This article provides an overview of the epidemiology, pathogenesis, clinical manifestations, diagnostic methods, and management of B19V infection during pregnancy.

Keywords: Anemia; Hydrops; Infection; Parvovirus B19; Prenatal.

Fig. 1

Number of acute B19V infections in pregnant women (data 2019 and 04/2024 from routine diagnostics in the Laboratory Enders, Germany) (adapted from Beck et al. 2024)

Fig. 2

Facial rash due to a parvovirus B19 infection

Fig. 3

Typical fetal extracardiac signs of a parvovirus B19 infection. The upper row of images shows fetal ascites (a), pericardial and minimal pleural effusions as well as skin edema (b), and hyperechogenic bowel (c). In the lower row, there is hepatomegaly (d), placentomegaly (e) and polyhydramnios (e)

Fig. 4

Typical fetal cardiac signs of a parvovirus B19 infection. The upper row of images shows a pericardial effusion (a) and cardiomegaly (b). The lower two images demonstrate tricuspid regurgitation by color Doppler (c) and spectral Doppler sonography (d)

Fig. 5

Increased peak velocity in a fetus with fetal anemia. The peak velocity is 52 cm/s which is significantly higher than the gestational age-related threshold of 1.5 MoM. The 1.5 MoM threshold in cm/s corresponds approximately to twice the gestational age in weeks (e.g., 19 weeks → 38 cm/s)

Fig. 6

Fetal anemia at 11 weeks’ gestation. The nuchal translucency measurement is increased (2.7 mm). The middle cerebral artery peak velocity appears to be increased, though a reliable threshold at this early gestational age has not been developed

Fig. 7

Intrauterine transfusion into the umbilical vein at the placental cord insertion (a) and into the intrahepatic portion umbilical vein (b)