Prevention of intrauterine infection by hepatitis B virus with hepatitis B immune globulin: efficacy and mechanism.

OBJECTIVE: To evaluate the efficacy of hepatitis B immune globulin (HBIG) in preventing intrauterine infection by hepatitis B virus (HBV) and to investigate its mechanism. METHODS: Forty-eight pregnant women positive for hepatitis B surface antigen (HBsAg) were randomly divided into 2 groups. The 34 women in the study group were injected with HBIG during pregnancy; the other 14 women were controls. Maternal blood samples were taken before HBIG injection and at delivery. Neonatal blood samples were taken within 24 hours after birth before HBIG and hepatitis B vaccine were given. HBsAg and antibody to HBsAg (anti-HBs) were tested by radioimmunoassay. RESULTS: None of the 35 newborns (including 2 twins) in the study group was positive for HBsAg, but 3 (21%) in the control group were positive (P = 0.02). The HBsAg titers in the women in the study group decreased after HBIG injection. Of the 35 newborns in the study group, 32 (91%) were positive for anti-HBs. CONCLUSION: Systematic injections of HBIG during pregnancy may prevent intrauterine HBV infection, the mechanism of which may be reduction of maternal HBV virernia and production of fetal passive immunity.