Mechanism of intrauterine infection of hepatitis B virus

AIM:To explore the possible mechanism of intrauterineinfection of hepatitis B virus (HBV).METHODS:HBV DNA was detected in vaginal secretionand amniotic fluid from 59 HBsAg-positive mothers and invenous blood of their newborns by PCR.HBsAg and HBcAgin placenta were determined by ABC immunohistochemistry.RESULTS:The rate of HBV intrauterine infection was 40.1%(24/59).HBV DNA was detected in 47.5% of amniotic fluidsamples and 52.5% of vaginal secretion samples respectively.HBsAg and HBcAg were detected in placentas from HBsAg-positive mothers.The concentration of the two antigensdecreased from the mother's side to the fetus's side,in thefollowing order:maternal decidual cells > trophoblastic cells>villous mesenchymal cells > villous capillary endothelialcells.However,in 4 placentas the distribution was in thereverse order.HBsAg and HBcAg were detected in amnioticepithelial cells from 32 mothers.CONCLUSION:The main route of HBV transmission frommother to fetus is transplacental,from the mother side ofplacenta to the fetus side.However,HBV intrauterineinfection may take place through other routes.