Parvovirus B19 Infection During Pregnancy

Introduction

Parvovirus B19 infection during pregnancy is rare, but potentially dangerous. In susceptible mothers, transplacental transmission of parvovirus B19 is possible. If acquired in utero , parvovirus B19 infection can lead to severe fetal anemia and myocarditis. In some instances, the infection may result in fetal death in the second or third trimester. Although in utero fetal infection is usually self-limited, severe cases are treated with intrauterine fetal blood transfusion to maintain fetal red blood cell levels until the fetus recovers from the infection.

Disorder

Prevalence and Epidemiology

Parvovirus B19, a single-stranded deoxyribonucleic acid (DNA) virus, is most commonly associated with erythema infectiosum (also referred to as fifth disease ). Although one-third of infections are asymptomatic, the virus may also cause maternal arthritis, aplastic crisis, and hydrops fetalis.

Parvovirus B19 is primarily transmitted by respiratory droplets and infected blood products. The patient is considered infectious 5 to 10 days after exposure and before the onset of a rash or other symptoms. When a rash erupts, the patient is no longer infectious. Approximately 50% to 60% of women of reproductive age have evidence of prior infection. The secondary attack rate for the household is approximately 50%. Susceptible individuals exposed in a classroom setting have a 20% to 30% chance of acquiring the disease. Of pregnant women, 40% to 50% are immune to parvovirus B19. The incidence of this acute infection in pregnancy ranges from 3%–4%. The risk of fetal transmission, which does not change with gestational age, is approximately 33%. The rate of fetal loss ranges from 2%–9% among women with serologically proven parvovirus B19 infection. However, fetal loss rate appears to be significantly higher if the disease is acquired before 20 weeks' gestation (11% versus <1%). Although immunity is lifelong, there have been reports of reinfection.

Etiology and Pathophysiology

The incubation period for parvovirus is 10 to 20 days. Manifestations of erythema infectiosum include low-grade fever, malaise, myalgias, arthralgias, and a “slapped cheek” facial rash. An erythematous, lacelike rash may extend onto the torso and upper extremities. In children, parvovirus infection can cause a transient aplastic crisis. An aplastic crisis may also occur in adults with an underlying hemoglobinopathy.

When maternal parvovirus infection occurs during pregnancy, the virus can cross the placenta and infect red blood cell progenitors in the fetal bone marrow. The virus attaches to the P antigen on red blood cell stem cells and suppresses erythropoiesis, resulting in severe anemia and high-output congestive heart failure. This same antigen is also present on fetal myocardial cells, and in some fetuses, the viral infection causes a cardiomyopathy that contributes further to heart failure. As long as fetal anemia is treated, spontaneous recovery is expected. Fetal complications are unlikely to occur more than 8 to 10 weeks after the initial exposure to the virus. Epidemiologic studies have failed to establish any association between parvovirus B19 infection and congenital malformations.

Manifestations of Disease

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