RISK OF INFECTION WITH PARVOVIRUS B19

Vertical transmission in pregnancy and fetal hydrops was first reported in 1984 (1,2). The risk of vertical transmission is approximately 33% (3).

• Fetal loss can occur at any age (3-6).
• Greatest risk of fetal loss is £20 weeks gestation (5).
• Fetal infection does not always result in fetal demise.
• About 50% of pregnant females are immune to parvovirus B19 and are therefore not at risk.
• Without known exposure, about 1% of pregnant women will develop laboratory evidence of infection during pregnancy (4).
• 5% of non-immune pregnant women with casual contact (e.g. school teachers), and 60% of those with household contacts will develop infection (5).
• Fetal transmission rate of parvovirus is estimated at 17-33% (3,6).

REFERENCES

1. Brown T, Anand A, Ritchie LD et.al. Intrauterine parvovirus infection associated with hydrops fetalis. Lancet 1984;2:1033-1034.
2. Knott PD, Welply GAC, Anderson MJ. Seriologically proved intrauterine infection with parvovirus. Br Med J 1984;189:1660.
3. Public Health Labratory Service Working Party on Fifth Disease: Prospective study of human parvovirus (B19) infection in pregnancy. Br Med J 1990;300:1166-1170.
4. Crane JMG. Prenatal exposure to viral infections. Can J of CME 1998;November:61-74.
5. Centers for Disease Control: Risks associated with human parvovirus B19 Infection. MMWR 1989;38:81-88,93-97.
6. Harger JH, Alder SP, Koch WC et.al. Prospective evaluation of 618 pregnant women exposed to parvovirus B19: Risks and symptoms. Obstet Gynecol 1998;91:413-420.