Risk of vertical transmission of hepatitis B after amniocentesis in HBs antigen-positive mothers

Background & Aims Despite appropriate immunoprophylaxis, HBV vertical transmission (VT) occurs in 5-10% of infants born to HBs-antigen (HBsAg)+ mothers. We investigated whether amniocentesis increases the risk of transmission. Methods We performed a case-control study on infants who were born to HBsAg+ mothers without antiviral exposure and completed appropriate immunization. Infants born to mothers with amniocentesis were compared to those without amniocentesis to assess VT rates, which were defined by the percentage of infants with HBsAg positivity when they were 7-12 months old. Results Of the 642 consecutive infants enrolled, 63 infants with amniocentesis were compared with 198 matched infants selected from the remaining 579 infants without amniocentesis. There was a higher VT rate in infants with amniocentesis than in those without amniocentesis (6.35% vs. 2.53%; p = 0.226). Maternal HBV DNA levels before amniocentesis were further stratified to <500 copies/ml, 500-6.99 log₁₀ copies/ml, and ≥7 log₁₀ copies/ml for subset analyses. There were no significant differences in the VT rates between the amniocentesis group and the control group if the maternal HBV DNA levels were <6.99 log₁₀ copies/ml. However, a significantly higher VT rate was observed in the amniocentesis group vs. the control group if the maternal HBV DNA levels were ≥7 log₁₀ copies/ml (50% vs. 4.5%, respectively, p = 0.006). According to baseline value risk analyses, performing amniocentesis on highly viremic mothers was a risk factor for HBV transmission (OR = 21.3, 95% CI: 2.960-153.775). Conclusions Amniocentesis performed on HBsAg+ mothers with HBV DNA ≥7 log₁₀ copies/ml significantly increased the frequency of VT. HBsAg+ women who plan to have amniocentesis should be evaluated for the risk of VT and stratified according to their HBV DNA levels. Further prospective studies are warranted to verify our findings.