Parvovirus B19 in pregnancy

Definition

Pathogen and Clinical Presentation

• In children, the disease is called: fifth disease, i.e., erythema infectiosum.
• Typical in children: malar erythema, lacy exanthem.
• What the virus attacks: erythroid progenitor cells.
• The fetus is therefore at risk of: aplastic anaemia, hydrops fetalis.
• Predominant in adults: arthralgia, flu-like course.
• The child is contagious: before the exanthem appears.

• Parvovirus B19 infection in pregnancy is a maternal infection with the agent of erythema infectiosum (fifth disease) that can be transmitted transplacentally to the fetus.

Occurrence & epidemiology

Epidemiology

• At the start of pregnancy, 34–65% of pregnant women are not immune, depending on the population studied.

Aetiopathogenesis

Aetiology and pathogenesis

• The virus is transmitted via respiratory secretions, hand-to-mouth contact, blood products and transplacentally.
• Fetal tissues, including haematopoietic cells and myocardium, express the viral P antigen receptor, which mainly explains anaemia and hydrops.
• The rate of transmission to the fetus is 17–33%.
• The fetus is most at risk in the first and second trimesters; after 20 weeks of gestation the risk of hydrops is 1% or less.

Clinical features

Clinical features and complications

• In immunocompetent adults, infection is usually asymptomatic or mild; maternal manifestations include erythema infectiosum, arthropathy, anaemia and thrombocytopenia.
• Fetal consequences include anaemia, thrombocytopenia, myocarditis, effusions, non-immune hydrops and intrauterine death; however, most infected fetuses remain unaffected.

Diagnosis

Fetal Monitoring

• The crucial measurement is: PSV in the middle cerebral artery (MCA).
• What causes it to increase in anaemia: lower blood viscosity.
• Threshold for a suspected diagnosis of severe anaemia: PSV increase above 1.5 MoM.
• Other signs on ultrasound: ascites, effusions, skin & placental edema.

• Maternal diagnosis is based on IgG and IgM antibodies; IgM is detectable from the end of the first week of infection.
• Fetal infection is detected by PCR of amniotic fluid.
• A middle cerebral artery peak systolic velocity above 1.5 MoM is highly suggestive of moderate to severe fetal anaemia.
• Ultrasound signs of hydrops are ascites, skin oedema, pleural and pericardial effusions and placental oedema.

Keep learning in the app

Further reading (selection)

1. J Pers Med 2024: Parvovirus B19 Infection and Pregnancy: Review of the Current Knowledge (PubMed Central)
2. DocCheck Flexikon, Ringelröteln

Cross-references