What are the consequences of Parvovirus B19 infection for the fetus?
Fetal anemia:

• Parvovirus B19 preferentially infects and replicates in erythroid cells.
• Active B19V infection causes fetal anemia.
• Anemia is an underlying factor in the development of hydrops, ascites and can lead to fetal loss.
• Non-immune hydrops fetalis (NIHF).
• Parvovirus B19 infection induces severe anemia which leads to NIHF.
• The most common form of hydrops is NIHF (~75% of cases).
• 10-20% of cases of idiopathic NIHF are B19V-associated(7).
• Hydrops usually occurs 2-4 weeks after maternal B19V infection(8).
• On average, there is a 10% risk of hydrops following B19V infection(10). 

Fetal loss :

• Up to 10% of Parvovirus B19 infections during pregnancy are associated with fetal loss(11).
• The majority of fetal losses due to B19V infection occur in the 2nd trimester.
• Fetal death usually occurs 4-6 weeks post infection but have been reported up to 12 weeks after symptomatic infection(1).
  

What are the consequences of Parvovirus B19 infection for the Mother?

• Most pregnant women are asymptomatic.
• Some may experience exanthem and arthralgia(9).
  

How can a woman at risk of infection be identified?

• Screening patients for their Parvovirus B19 antibody status will identify a patient at risk of infection.
• A variety of diagnostic assays are available to detect the presence of IgM and IgG antibodies in serum.
  

• Through screening and assessing pregnant women.
• By treatment of women infected with Parvovirus B19.
• Through education of pregnant women about Parvovirus B19.

How can screening for Parvovirus B19 infection before or during pregnancy be of help?

• Appropriate patient management is dependent on accurate B19V diagnosis.
• Screening patients for B19V antibody status will determine the need for further follow-up.
• An IgG-positive, IgM-negative patient should be reassured that Parvovirus B19 infection is not a cause for concern during their pregnancy.
   

What are the treatment options for Parvovirus B19 infection during pregnancy?

• For moderate to severe hydrops, fetal blood sampling may be appropriate.
• If the reticulocyte count is high, marrow aplasia is already in the resolution stage and hydrops should resolve without therapy.
• If hydrops develops, an intrauterine blood transfusion via cordocentesis should be considered(12).
• The severely anemic fetus with a low reticulocyte count may benefit from immediate transfusion.
• High-titre intravenous immunoglobulin has been reported to be an effective therapy (12).
• Ultra-sound exams should be performed every 1-2 weeks for up to 6-8 weeks.
• The algorithm of care shown in the "diagnosis" section outlines treatment options based on serology assay results.  

How will education regarding Parvovirus B19 infection be of help to the pregnant woman?

• It will allow them to avoid situations that involve possible risk of exposure.
• Patient monitoring of fetal movement would also serve as an important aid to fetal surveillance in women beyond gestation week 28.
• In summary, as in all care, diagnosis, screening and education are key to successful patient management. Selecting a test that ensures this is critical. Ask your lab about the Biotrin Parvovirus B19 assay.

References:

1. Hedrick J. The effects of human parvovirus B19 and cytomegalovirus during pregnancy.
   J Perinatol Neonat Nurs. 1996; 10:30-39.
   
2. Public Health Laboratory Service Working Party of Fifth Disease. Prospective study of human parvovirus (B19) infection in pregnancy. Br J Med. 1990; 300:166-70.
   
3. Anderson LJ, et al. Risk of infection following exposures to human parvovirus B19. Behring Inst Mitt. 1990; 85:60-3.
   
4. Valeur-Jensen AK, et al. Risk factors for parvovirus B19 infection in pregnancy. JAMA 1999; 281:1099-105
   Gay NJ, et al.
   
5. Age Specific Antibody Prevalence to parvovirus B19: How many women are infected in pregnancy?
   Communicable Disease Report 1994;4:104-107.
   
6. Eis-Hübinger AM, et al. Parvovirus B19 infection in pregnancy. Intervirology 1998;41:178-84.
   
7. Jordan J. Identification of human parvovirus B19 infection in idiopathic nonimmune hydrops fetalis. Am J Obstet Gynecol. 1996;174:37-42.
   
8. Yaegashi N, et al. The frequency of human parvovirus B19 infection in nonimmune hydrops fetalis. J Perinat Med. 1994; 22:159-63.
   
9. Komischke K, Searle K and Enders G. Maternal serum alpha-fetoprotein and human chorionic gonadotropin in pregnant women with acute parvovirus B19 infection with and without fetal complications. Prenat Diagn. 1997; 17:1039-46.
   
10. Yaegashi N, et al. Serologic study of human Parvovirus B19 infection in pregnancy in Japan. J Infect 1999; 38:30-5.
    
11. Wattre P, et al. A clinical and epidemiological study of human parvovirus B19 infection in fetal hydrops using PCR Southern blot hybridization and chemiluminescence detection. J Med Virol. 1998; 54:140-4.
    
12. Alger LS: Toxoplasmosis and Parvovirus B19. Infect Dis Clin North Am. 1997; 11:55-75.