Serological Investigation of the possibility of congenital transmission of papovavirus JC.

In an examination of paired sera from pregnant women, 9 of 57 women who had JC virus antibodies in their first specimens exhibited virus reactivation, as judged by a fourfold or greater rise in JC virus hemagglutination-inhibiting antibodies; 43 women remained seronegative through pregnancy. JC virus-specific immunoglobulin M was not demonstrated in umbilical cord sera of six infants born to mothers showing reactivation or in 300 additional umbilical cord sera from normal pregnancies.