Prospective study of human parvovirus (B19) infection in pregnancy. Public Health Laboratory Service Working Party on Fifth Disease.

OBJECTIVE: To determine the fetal infection rate and outcome of pregnancy among women who acquire infection with human parvovirus (B19) in the antenatal period.

DESIGN: Prospective study of infected pregnancies till time of delivery or abortion with virological investigation of fetuses, neonates, and 1 year old infants.

SETTING: England and Wales during 1985-8.

PATIENTS: 190 Pregnant women with serologically confirmed B19 infection in pregnancy, their fetuses, neonates, and 1 year old infants.

RESULTS: Of 186 mothers who elected to go to term, 156 (84%) delivered a normal baby. Follow up of 114 of these infants to the age of 1 year disclosed no appreciable abnormalities, although 27 had serological evidence of intrauterine infection. The overall fetal loss rate (30 cases; 16%) was similar to that in an uninfected antenatal sample (unmatched), but there was a pronounced excess of fetal loss in the second trimester in the B19 infected mothers (11.8%; 95% confidence interval 6.8% to 17.8%). Based on virological findings in the aborted fetuses the risk of fetal death due to B19 in an infected pregnancy was estimated to be 9%. The transplacental transmission rate was estimated to be 33%.

CONCLUSIONS: Most women with B19 infection in pregnancy had a satisfactory outcome, but there was nevertheless a substantial risk of fetal loss in the second trimester. In view of the absence to date of any evidence of damage to babies who survive maternal infection therapeutic termination of pregnancy is not indicated.