Objective: To study the possible mechanism of intrauterine infection of hepatitis B virus (HBV).
Methods: HBV DNA was examined in amniotic fluid, and vaginal secretion of 59 HBsAg positive mothers and in cord blood of their neonates by PCR. Ten negative hepatitis B virus marker (HBVM) mothers and their neonates were served as control. HBsAg and HBcAg in placenta were examined by avidin biotin complex (ABC) method.
Results: The detection rate of HBV DNA in amniotic fluid, vaginal secretion and neonatal cord blood of the study group were 47.5% (28/59), 52.5% (31/59) and 45.8% (27/59) respectively. HBsAg and HBcAg in placenta was distributed in the following descending order: maternal decidual cells, trophoblastic cells, villous mesenchymal cells and villous capillary endothelial cells. But the distribution was in reverse order in 4 placentas. HBsAg and HBcAg were detected in amniotic epithelial cells in 32 mothers.
Conclusion: The main route of HBV transmission from mother to fetus is transplacental, from maternal side of placenta to fetal side. However, HBV intrauterine infection may take place through other routes.