Development of occult hepatitis B viral infection in pregnancy: implications for antenatal screening in women from endemic areas.

Occult hepatitis B virus (HBV) infection, manifest clinically by the presence of HBV deoxyribonucleic acid (HBV DNA) in peripheral blood in individuals who test negative for the HBV surface antigen (HBsAg), may occur in various clinical contexts, including under the influence of pharmacological immunosuppression in patients from areas endemic for HBV and, hence, at risk of previous exposure. Pregnancy is a condition associated with immune suppression, but whether virus-specific immunity may be suppressed to an extent sufficient to allow occult HBV infection to develop is currently unknown. This is potentially relevant not only to the mother's health but also because vertical transmission has been reported in the occult HBV infection setting. We report a 30-year-old woman from a country endemic for HBV who, prior to pregnancy, was persistently HBsAg-negative with undetectable HBV DNA in peripheral blood, in whom HBV DNA became increasingly detectable during pregnancy, peaking in the third trimester, before returning to undetectable levels postpartum. HBsAg remained negative and liver function tests were normal throughout. Immunoglobulin M hepatitis B core antibody, a marker of the possibility of acquisition of a new HBV infection, was also negative. The baby received immunization against HBV infection from birth and has remained HBV negative at six months. This report documents for the first time that occult HBV infection may develop during pregnancy. Further data are required regarding the prevalence of this phenomenon, predisposing factors, impact on maternal health and risk of vertical transmission so that implications for current antenatal screening strategies that do not include measurement of HBV DNA in peripheral blood can be properly determined.