Hepatitis B surface antigen and chronic hepatitis in infants born to asymptomatic carrier mothers.

Twenty-three infants born to asymptomatic hepatitis B surface antigen (HBSAg) carrier mothers were followed up to determine the vertical transmission of hepatitis B virus. Four infants became positive for HBSAg within four months after birth. Three showed hepatic dysfunction; liver biopsy specimens demonstrated mild chronic hepatitis in one and persistent hepatitis in another. In six infants followed up for more than six months after birth, antibody to HBSAg (anti-HBS) without antigenemia could be detected. Antigenemia of cord blood strongly suggested that hepatitis B viral infection of the infant would occur. HBSAg was also demonstrated in breast milk by radioimmunoassay in three cases. These findings indicate that vertical transmission of hepatitis B virus occurs in many infants born to asymptomatic HBSAg carrier mothers, and that some of them become persistent carriers or develop chronic hepatitis without showing any signs suggesting hepatic involvement.