Data of mothers were collected from medical records that included complete healthcare information before and after delivery. Each infant was consecutively followed up after birth, growth index (weight, length and head circumference), feeding patterns and serum level of HBV DNA and viral markers were recorded. Serum HBV markers (HBsAg, HBsAb, HBeAg, and HBcAb) titers、HBV DNA load and liver function of mothers were regularly measured during pregnancy. Serum HBsAg, HBsAb titer and HBV DNA load of infants were tested at birth, the age of 7 and 12 months. Placental tissue sections were used for immunohistochemical staining of HBsAg (mouse, 1:50, ZM-0122, Beijing Zhongshan Golden Bridge Biotechnology Co.), HBIG (rabbit, 4.7 mg/ml, 1:2500, prepared as described above), and CD68 (mouse, 1:25, ab955, Abcam).