Evidence for transplacental transmission of Ross River virus in humans.

Immunoglobulin M antibody to Ross River virus was found in the cord blood of 11 368 children born to mothers who were pregnant during the epidemic of Ross River virus infection in Fiji, in 1979. Since IgM antibody does not normally cross the human placenta, these findings are suggestive of in-utero infection. Antibody to Ross River virus was also present in eight of the 11 mothers of children with IgM-positive cord blood. One of the mothers with IgM-negative blood had no detectable haemagglutination-inhibiting antibody to Ross River virus. All children appeared normal at birth.