Mechanisms of maternal-fetal transmission of hepatitis B virus.

In a prospective study of maternal-fetal transmission of hepatitis B virus in 125 healthy mothers who were carriers of hepatitis B surface antigen (HBsAg), preliminary results showed that the most important determinant in such transmission was the presence of hepatitis B e antigen in the mother. HBsAg was detectable by solid-phase radioimmunoassay in 33% of amniotic fluid samples, 50% of cord blood samples, 71% of breast milk samples, and 95.3% of samples of gastric contents from newborns. The presence of HBsAg in gastric aspirate from the infants immediately after birth in almost all cases suggests a universal mechanism of infection by the oral route during delivery. In light of these findings, precautions such as possible elective cesarean section, routine gastric aspiration of the newborn, avoidance of breast-feeding, etc., should be taken to avoid perinatal transmission.