It is advisable for pregnant women to test for Hep B so if they are infected they can prevent passing the infection to their unborn child. Usually it is passed during delivery through exposure to body fluids. Drugs given to the mother during pregnancy and to the child after birth can prevent transmission of the virus to the child. Hep B is not passed by breastfeeding. Ask your doctor for advice.
Attribution: Straight Talk Foundation & Marie Stopes