Background  For women with hepatitis B virus (HBV) infection, little is known about the natural progression of the disease during pregnancy or its impact on pregnancy outcomes.

Objectives  To investigate the natural progression of HBV infection during pregnancy or its impact on pregnancy outcomes.

Methods  In this retrospective cohort study, we reviewed medical records of all patients who were pregnant and presented with HBsAg-positivity between 2000 and 2008 at a community gastroenterology practice and a university hepatology clinic. Maternal characteristics were analysed according to maternal and perinatal outcomes.

Results  A total of 29 cases with at least 2 measurements of either HBV DNA or alanine aminotransferase (ALT) levels were included. Older age was the only predictor of a trend towards higher risk of an adverse clinical outcome [OR = 1.21 (0.97–1.51), = 0.089], defined as either a negative foetal outcome (premature delivery, spontaneous abortion), or a negative maternal outcomes (gestational diabetes mellitus, pre-eclampsia, hepatic flare, liver failure). This trend for age remained even after adjusting for baseline ALT. Baseline serum HBV DNA, ALT, hepatitis B e antigen status, gravida and parity were not significant predictors for adverse clinical outcomes. Four patients developed liver failure.

Conclusions  Maternal and neonatal outcomes are highly variable in this clinic-based patient cohort. Severe complications due to HBV infection can occur during pregnancy in previously asymptomatic patients. It is unclear how generalizable the results observed in this cohort would be to the general population; therefore, further studies are needed to identify reliable predictors for significant adverse outcomes and until more data are available, pregnant patients with HBV infection should be monitored with periodic serum HBV DNA and ALT levels.