Many women are concerned about the impact of hepatitis B on pregnancy. In general, the impact of hepatitis B on pregnancy lies in two aspects: first, the risk of transmission to the baby; second, the impact on the pregnant woman herself and the pregnancy. 1, the risk of transmission of hepatitis B to the baby: mother-to-child vertical transmission is currently the main route of transmission of chronic HBV infection in China. Vertical transmission from mother to child includes 3 levels of infection: in utero infection, perinatal infection, lactation infection. Intrauterine infection refers to the infection in the fetal organism caused by HBV transmission through the placenta. Studies have shown that risk factors for in utero infection include maternal serum HBeAg positivity, high HBsAg titers, high HBV DNA levels (e.g., HBV DNA ≥ 108copies/m1), and preterm delivery of the mother during pregnancy. If the mother’s serum HBV DNA ≥ 108copi, the rate of vertical transmission from mother to child after birth is as high as 8.5%, even with standard active and passive immunoprophylaxis. Perinatal infection refers to fetal infection from exposure to maternal vaginal secretions and maternal blood, and is an important route of transmission. The current active and passive immunization of newborns is mainly to minimize perinatal infections and lactation infections, which can reduce the infection rate by 80% to 95%, but it is difficult to interrupt the infection in utero. Therefore, neonatal immunoprophylaxis cannot completely interrupt vertical transmission from mother to child. Therefore, pregnant women with HBV DNA ≥ 108copi need to fully consider the need for antiviral therapy. 2. Effects on pregnant women themselves and pregnancy: (1) Chronic hepatitis B may have adverse effects on pregnancy. Chronic HBV infection is associated with gestational diabetes, prenatal hemorrhage, preterm labor, and reduced fetal Apgar score. If the mother has severe liver function abnormalities, she is prone to postpartum hemorrhage, increased chances of puerperal infection, low fetal weight, fetal distress, preterm delivery, stillbirth, and neonatal asphyxia. (2) Pregnancy may aggravate chronic hepatitis B. During pregnancy, a series of physiological changes occur in the mother, which can increase the burden of existing liver disease and aggravate liver damage. For example, maternal immune tolerance during pregnancy may lead to an increase in hepatitis viral load; maternal metabolism is high, nutrients are consumed, the mother produces a large amount of sex hormones that need to be metabolized and inactivated in the liver during pregnancy, and fetal metabolism and detoxification also depend on the maternal liver to complete. All of these add to the burden on the liver and may lead to aggravation of liver disease. Therefore, hepatitis B has a very important impact on pregnancy. Pregnant women who are planning to become pregnant or are already pregnant should undergo hepatitis B related tests (e.g. liver function, hepatitis B virus DNA quantification, etc.) at a hepatitis specialist for a thorough assessment of the need for antiviral treatment.