Vertical transmission of the hepatitis B surface antigen in Thailand.

The vertical transmission of the hepatitis B surface antigen (HBsAG) from HBsAg carrier mothers to their infants and children were studied in 42 mother-infant pairs, 27 siblings aged under 5 years and 34 fathers of these families. Thirteen out of 42 (30.9%) infants born from these mothers became HBsAg carriers at 3 to 6 months of age. Vertical transmission to their infants (76.5%) and other siblings (88.9%) occurred only in those mothers with e-antigen (HBeAg) positive but none in HBsAg carrier mothers without HBeAg. Most of the HBsAg carrier babies (70.5%) and their siblings (77.7%) born from the carrier mothers with HBeAg positive also had HBeAg in their sera. Good correlation of the presence of HBeAg and higher titer of HBsAg was found both in HBsAg carrier mothers and in their off-springs. This study clearly shows that HBsAg carrier Thai mothers with HBeAg transmitted hepatitis B virus vertically to their infants and children more readily than do the HBsAg carrier mothers without HBeAg.