The fifth disease: Erythema Infectiosum (slapped cheek syndrome). 50-75% of women at reproductive age are immune. Epidemics every 3-6 years. Seroconvertion 13% during epidemic and 1% if no epidemic. Background: Infection affects the bone marrow and can cause anemia especially among fetus which can cause hydrops. Diagnosis: Flue like symptoms followed 1-4 days rash (not at all get it) and 30% arthritis like joint involvement. IgM 3 days after the symptoms and persist 3-4 months. IgG after 7 days. Incubation period 1-3 weeks. Infection before symptoms and probably not infection after onset of rash and arthritis like symptoms. IGM positive the diagnosis is confirmed. IgG only positive no infection the last 4-6 weeks. If IgG and IgM are both negative, repeat test within 2-3 weeks. Infection in the fetus can be confermed by Parvovirus DNA. Risk: No risk for malformation. The transmission rate is the risk for infection is 50% in families, teachers 20-30%. The risk of fetal death is largely confined to maternal infection within the first 20 weeks. Fetal death presented in the first 16 weeks are most often not accompanied by hydrops. The peak incidence of Parvo-virus associated hydrops-foetalis is between week 17 and 24. Risk for fetal demise less than 3% and highest in second trimester. Risk up to 10 weeks after infection usually within 3-6 weeks. The risk for fetal hydrops is 2-4%. The risk for hydrops decrease after 20 weeks and is 2-4 % before 32 weeks and less than 1 % after 32 weeks. The risk of fetal death is very small after 20 weeks. Fetal anemia causing ascitis and/or hydrops. Hydrops further caused by myocarditis, hypo-albuminemia (liver damage) and venous obstruction caused by placenta-edema and liver enlargement. Fetal Hgb in hydropics range from 2.1-9.6. Spontaneous resolution occur in 30% but a rare events in severe hydrops. Handling: Sero-negative women should not work in child institution when there is an epidemic but stay home until 6 weeks after the last child has had symptoms. In case of infection. Ultrasound every second week until 10 weeks after infection to see if the child develops ascites/hydrops mean 6 weeks or until 30 weeks. In severe cases, intrauterine infusion with survival 85% mild to moderate, hydrops disappear spontaneously in 50% of cases. Few cases describe in which anaplastic anemia has been observed in infants treated by intrauterine transfusion. Intrauterine death is also seen without development of ascitis/hydrops. Therefor many advocated for parvovirus DNA analysis No indication for termination. References: (1) Crane J. Parvovirus B19 Infection in Pregnancy. SOGC Clinical Practice Guidelines No. 119. September 2002. (2) Enders M, Weidner A, Zoellner I, Searle K, Enders G. Fetal morbidity and mortality after acute human parvovirus B19 infection in pregnancy: prospective evaluation of 1018 cases. Prenat Diagn 2004;24:513-18 3) www Infpreg.com 4) www.uptodate.com 2007 UpToDate version 13,1 2005
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