The rates of positive surface antigen in maternal secretions from the birth canal, blood and amniotic fluid for hepatitis B were 98%, 100% and 33%, respectively. The rate of hepatitis B surface antigen positivity in the stomach and oropharyngeal contents of newborns was above 95%. Therefore, the fetus swallowing toxic blood, amniotic fluid and secretions from the birth canal is objective evidence of neonatal infection. Meanwhile, the existence of intrauterine infection with hepatitis B virus has been confirmed by various experimental methods and scientific control observations, and the total rate of intrauterine infection is considered to be around 10%. It has been demonstrated that hepatitis B virus can cause intrauterine infection in the fetus directly through the placental barrier before the fetus is born. Whether caesarean section can reduce the rate of postnatal hepatitis B surface antigen conversion in infants, 447 infants born to mothers who were double positive for hepatitis B surface antigen and e antigen in Taiwan were immunized using the 0, 1, 6 procedure. After one year, the hepatitis B surface antigen conversion rate was found to be 24.1% in 385 children delivered spontaneously through the birth canal; the conversion rate was 97% in 62 children delivered by cesarean section