What are the routes of mother-to-child transmission of hepatitis B? Intrauterine transmission: The infant is infected with hepatitis B virus through the blood circulation in the mother. This mode of vertical transmission generally does not exceed 10%, and failure of mother-to-child blockade usually occurs in cases of intrauterine infection. Intrapartum transmission: The virus in the mother’s blood enters the umbilical cord blood through the ruptured placenta and enters the newborn when the baby’s skin or mucous membrane is abraded during delivery or when the placenta is absconded. Horizontal transmission: Close contact between the infant and the mother without appropriate immunization measures, breastfeeding in the presence of both nipples and broken mucous membranes in the infant’s mouth can transmit the hepatitis B virus.