Transplacental leakage of HBeAg-positive maternal blood as the most likely route in causing intrauterine infection with hepatitis B virus.

Thirty-two HBeAg-positive carrier mothers and their 32 babies were investigated to elucidate the mechanism involved in intrauterine infection with HBV. Five mothers had symptoms and signs of threatened abortion and/or threatened preterm labor. Three mothers gave birth more than 6 weeks after the episodes, and their babies were those infected in utero. The other two gave birth within 1 week after the episodes, and the two babies were treated with HBIG immediately after birth; HBV infection was successfully prevented. Therefore we suggest that transplacental leakage of HBeAg-positive maternal blood, which is induced by uterine contractions during pregnancy and the disruption of placental barriers, is the most likely route to cause HBV intrauterine infection.