Transmission of hepatitis B virus (HBV) from mother-to-infant is the predominant route in most high prevalence areas such as China. However, father-to-child transmission also plays another important role in the prevalence of hepatitis B. Children infected with HBV from their carrier fathers would be horizontally by postnatal intimate contact or vertically via male germ line. The latter is considered an intrauterine infection, however, whether it is really existed in human remains to be determined.