Hepatitis B virus infection among pregnant women delivering at Harare Maternity Hospital, Harare Zimbabwe, 1996 to 1997. 
To determine the prevalence of hepatitis B virus (HBV) carrier and infectivity status among pregnant women delivering at Harare Maternity Hospital.  A serological survey study of pregnant women admitted for labour and delivery.  Harare Maternity Hospital, Harare, Zimbabwe between June 1996 and June 1997.  A random sample of 1,000 women, delivering at the hospital during the study period agreed to participate in the study.  Serum samples were available for 984 women.  HBV carriage status was determined by the presence of hepatitis B surface antigen (HBsAg) by enzyme immunoassay (EIA).  Maternal HBV infectivity status was determined by testing all HBsAg positive women for the presence of hepatitis e surface antigen (HBeAg) using EIA.  Overall 246 (25%) women were identified as carriers of HBV (95% confidence interval 22 to 28%).  The frequency of HBV carriers did not vary with maternal age, parity or marital status.  Only a positive prior history of spontaneous abortion was associated with an increased prevalence of HBV carriage status.  Eight of the 246 (3.3%) women identified as HBV carriers tested positive for HBeAg.  Hence, 0.8% of the entire study population was found to be at high risk of transmitting HBV to their newborns.  Our results demonstrate a high prevalence of HBV carriage among women giving birth at Harare Maternity Hospital.  None of the demographic variables studied were important predictors of HBV carriage status.  The high carriage rate and low infectivity rates suggest that HBV infection is likely to be acquired by horizontal, rather than by vertical means of transmission.  Given the scarcity of financial resources, routine testing of mothers for HBsAg may not be feasible.  Our results suggest, however, that mass vaccination of all infants, irrespective of maternal HBV carriage status, may be the most effective approach to HBV prevention and control in Zimbabwe.