Perinatal transmission of hepatitis B virus: an Australian experience

Objective: To determine the rate of perinatal hepatitis B virus (HBV) transmission in an Australian setting and to identify maternal virological factors associated with highest risk of transmission. Design, participants and setting: A prospective, observational study of perinatal transmission of HBV. Participants were pregnant women attending Sydney South West Area Health Service antenatal clinics who tested positive for hepatitis B surface antigen (HBsAg), and their babies. All babies were routinely offered hepatitis B immunoglobulin (HBIG) and HBV vaccination. Babies positive for HBsAg at 9‐month follow‐up underwent further virological testing, including HBV DNA sequencing. The study was conducted between August 2002 and May 2008. Main outcome measures: HBV DNA levels and demographic characteristics of HBsAg‐positive pregnant women; proportion of their infants with active HBV infection at 9‐month follow‐up; maternal characteristics affecting transmission rate; HBV DNA sequencing of infected infants and their mothers. Results: Of 313 HBsAg‐positive pregnant women, 213 (68%) were HBV DNA‐positive and 92 (29%) were positive for hepatitis B “e” antigen (HBeAg); 138 babies born to HBV DNA‐positive mothers were tested for HBV infection (HBsAg positivity) at about 9 months of age. Four cases of transmission were identified. All four mothers had very high HBV DNA levels (> 108 copies/mL) and were HBeAg‐positive. Three of the four infants were infected with wild‐type HBV strains, with identical maternal/infant isolates. The fourth mother–infant pair had an S gene variant, HBV D144E, which has been previously reported in association with vaccine/HBIG escape. (Unfortunately, HBIG was inadvertently omitted from the immunisation schedule of this infant.) Transmission rates were 4/138 (3%) from HBV DNA‐positive mothers overall, 4/61 (7%) from HBeAg‐positive mothers, and 4/47 (9%) from mothers with very high HBV DNA levels. No transmission was seen in 91 babies of mothers with HBV DNA levels