Intrauterine transmission of hepatitis B virus is closely related to placental leakage.

Hepatitis B virus (HBV), transmitted by hepatitis B e antigen (HBeAg)-positive mothers by intrauterine infection, infecting newborns, is closely related to signs and symptoms associated with miscarriage. However, no correlation was observed between intrauterine infection of infants and the presence of antibodies of immunoglobulin M (IgM) class antibodies against hepatitis B core antigen (anti-HBc) in maternal blood, nor was HBeAg found in maternal or cord sera. These results indicate that contamination by the mother's blood, through placental leakage, plays an important role in HBV infection in utero. Without placental leakage, maternal blood could not pass through the placenta and enter fetal circulation, and so intrauterine infection would not occur, even if very high titers of hepatitis B surface antigen (HBsAg) and HBeAg were present in maternal blood.