Fetal parvovirus B19 infection

Parvovirus B19 infection during pregnancy causes up to 27% cases of non-imm une hydrops in anatomically normal fetuses. The virus is believed to cause arrest of maturation of red blood cell precursors at the late normoblast st age and also causes a decrease in the number of platelets. Fetal anemia is presently thought to be responsible for the development of skin edema and e ffusions. Myocarditis leading to heart failure may contribute to the develo pment of fetal hydrops. We reviewed the literature regarding prevalence, tr ansmission rates, clinical presentation, diagnostic techniques, current inv asive vs. conservative management options, outcome and postmortem findings in a total of 82 studies involving 230 invasively and 435 conservatively ma naged pregnancies. In this non-selected population, the proportion of seron egative susceptible mothers ranged from 19 to 65%, seroconversion with an i ncubation time of up to 20 days occurred in 5.7-12.1%, and 188/230 (82%) wh o were transfused infected fetuses bad a normal outcome as opposed to only 239/435 (55%) in the conservatively managed group. The average time from di agnosis to resolution in both groups was 6 weeks (range, 3-12 and 2-12 week s, respectively). The most promising diagnostic techniques were PCR of amni otic fluid or fetal blood and electron microscopy. There are some reports o f fetal abnormalities occurring (probably coincidentally) in cases of parvo virus, but the majority of postmortem findings were infection-related, in p articular myocarditis and hepatic abnormalities. Although management guidel ines cannot be derived from this study due to the variable degree of hydrop s in the analyzed studies, the present data suggest a benefit of transfusio n therapy over conservative management in infected fetuses. The only study which was corrected for severity of hydrops using ultrasound criteria showe d a clear benefit of intrauterine transfusion.