IMMEDIATE AND LONG-TERM OUTCOME OF HUMAN PARVOVIRUS B19 INFECTION IN PREGNANCY

Objective To estimate more precisely the risk of fetal loss and congen ital abnormalities after maternal parvovirus B19 infection, and to ass ess the long term outcome for surviving infants. Design Prospective co hort study of pregnant women with confirmed B19 infection with follow up of the surviving infants, The rate of fetal loss in the study cohor t was compared with that in pregnant women with varicella. Setting Cas es reported by laboratories in England and Wales between 1985-1988 and 1992-1995. Sample Four hundred and twenty-seven pregnant women with B 19 infection and 367 surviving infants of whom 129 were followed up at 7-10 years of age. Methods Questionnaires to obstetricians and genera l practitioners on outcome of pregnancy and health of surviving infant s. Maternal infection confirmed by B19-specific IgM assay and/or IgG s eroconversion. Results The excess rate of fetal loss in women with B19 infection was confined to the first 20 weeks of gestation and average d 9%. Seven cases of fetal hydrops followed maternal infections betwee n 9 and 20 weeks of gestation (observed risk 2.9%, 95% CI 1.2-5.9). No abnormalities attributable to B19 infection were found at birth in su rviving infants (observed risk 0%, upper 95% CI 0.86%). No late effect s were found at 7-10 years. Conclusions Around 1 in 10 women infected before 20 weeks of gestation will suffer a fetal loss due to B19. The risk of an ad-verse outcome of pregnancy after this stage is remote. I nfected women can be reassured that the maximum possible risk of a con genital abnormality due to B19 is under 1% and that long term developm ent will be normal.