This retrospective cohort study was performed to examine the relationship between maternal hepatitis B virus infection, as indicated by the surface antigen status, with the development of gestational diabetes mellitus in a normal-risk Chinese obstetric population. Maternal demographics, risk factors, and pregnancy outcome of 13,683 singleton pregnancies delivering in 1998-2001 were analysed according to maternal hepatitis B surface antigen status, which was routinely screened. Multiple logistic regression analysis was performed to examine the role of hepatitis B infection in the development of gestational diabetes mellitus. The 1138 women (8.3%) with hepatitis B infection had lower mean weight and body mass index, similar prevalence of chronic medical diseases and smokers, but increased prevalence of gestational diabetes mellitus, which remained significant (odds ratio 1.24, 95% confidence interval 1.01-1.51) after adjustment for confounding variables. However, there was no difference in pregnancy outcome. Our results confirmed the independent association between hepatitis B infection with gestational diabetes mellitus. The magnitude of chronic hepatitis B infection in the developing world and certain ethnic groups could have contributed to the high prevalence of gestational and possibly type 2 diabetes in these populations. Further studies on the long-term implications of our finding are warranted.