Hepatitis B Surface Antigen (HBsAg) is a protein found on the surface of the hepatitis B virus (HBV). It is used as a marker to detect an active HBV infection. The presence of HBsAg in the blood indicates that the person is infectious and can transmit the virus to others. In the context of Gynecology, understanding HBsAg status is crucial for managing pregnant women and preventing vertical transmission of HBV to the newborn.
