Prevention of vertical transmission of hepatitis B. The place of routine screening in antenatal care, and the case for immunization of infants at risk.

Many chronic carriers of hepatitis B virus acquire the infection from their mothers at birth; the risk is greatest if the mother either has acute hepatitis B or is a hepatitis Be antigen (HBeAg)-positive HBsAg carrier, but there is some risk also to the infants of mothers who do not carry HBeAg. At the Royal Women's Hospital, Melbourne, nearly 2% of women attending antenatal clinics are found to be carriers and, without immunization, approximately five infants per 1000 infants delivered (up to 15 infants annually) would also become carriers. Vertical transmission of hepatitis B can be prevented by a combination of passive and active immunization if infants at risk can be identified at or before birth. Routine screening for hepatitis B surface antigen in pregnant women is recommended, at least in institutions in which the patient population includes a high proportion of migrants, in whom the prevalence of hepatitis B carriage is relatively high.