Chronic hepatitis B virus (HBV) infection and its associated diseases seriously endanger the health of our residents. Chronic HBV infection refers to a state where hepatitis B surface antigen (HBsAg) positivity persists for more than 6 months, and if liver function is normal, it is called chronic HBV carriage (also known as HBV carriage); if liver function is abnormal, it is chronic hepatitis B. Therefore, the difference between chronic HBV carriage and chronic hepatitis B only lies in whether the liver function is abnormal or not. Most perinatal HBV infections in fetuses and newborns will become chronic, so perinatal prevention is the key to controlling chronic HBV infection. HBV is transmitted mainly through blood and other body fluids entering the body via broken skin or mucous membranes (including sexual transmission); ordinary contact or gathering for meals does not cause transmission. HBV transmission occurs mainly during delivery of the newborn and intimate contact with the mother after birth, and infection by this route can be prevented. The true intrauterine infection rate is <5%, and there is a lack of effective preventive measures. I. Prevention for newborns of HBsAg negative mothers: When the mother is HBsAg negative, regardless of HBV-related antibodies, there is usually no HBV in the body, and the preventive measures for newborns are: the first dose of hepatitis B vaccine after birth, followed by another dose one month and six months apart, i.e., the "0, 1, 6" program. There is no need to use hepatitis B immunoglobulin. Prevention of newborns of HBsAg positive mothers: If the mother is HBsAg positive, whether by cesarean section or vaginal delivery, the newborn is bound to be exposed to HBV, and cesarean section does not reduce mother-to-child transmission of HBV. It is imperative that newborns of HBsAg-positive mothers receive intra-muscular injection of 100 IU of hepatitis B immunoglobulin within 24 hours of birth, preferably within 12 hours of birth, as well as hepatitis B vaccination at different sites within 24 hours of birth, with the vaccine dose doubled. A second injection of hepatitis B immunoglobulin is usually not necessary. Immunoprophylaxis for preterm infants: Premature infants have immature immune systems and weak immune responses to vaccines, so they need to be boosted on the basis of routine hepatitis B vaccination. If a premature infant of HBsAg-negative mother is born with stable vital signs and can breastfeed normally, he/she can be vaccinated according to the "0,1,6" protocol without waiting until his/her weight reaches 2500g, and then receive a booster shot at 12 months of age; if the premature infant's vital signs are unstable, he/she should first be treated for relevant diseases and then receive vaccination according to the above protocol after stabilization. The vaccination is the same as that for preterm infants of HBsAg-negative mothers. Prevention for newborns whose mothers are HBsAg negative but whose fathers or other family members are HBsAg positive: If the mother is HBsAg negative, her newborn is not exposed to HBV during delivery, so the prevention of HBV infection requires vaccination according to the "0,1,6" protocol, and no injection of hepatitis B immunoglobulin is required. If the newborn is born in the care of a family member who is primarily a carrier of HBV, it is best to give the newborn 100 IU of hepatitis B immune globulin in addition to the vaccine. Although HBV DNA has been reported to be detected in semen, there is no evidence that semen can cause chronic HBV infection in the next generation. V. Breastfeeding by HBsAg-positive mothers: Although HBsAg and HBV DNA have been reported to be detectable in breast milk, breastfeeding does not increase the risk of HBV infection in newborns after formal post-exposure prophylaxis has been taken. VI. Feasibility of using hepatitis B immunoglobulin in late pregnancy to prevent intrauterine infection: Chinese scholars first proposed in 1995 that the use of hepatitis B immunoglobulin in HBV-carrying pregnant women in late pregnancy could prevent intrauterine infection, but subsequent studies confirmed that the use of hepatitis B immunoglobulin in late pregnancy was similar to the rate of chronic HBV infection in infants and children with routine post-exposure prophylaxis. Therefore, the idea that the use of hepatitis B immunoglobulin in late pregnancy prevents intrauterine HBV infection is not well founded and cannot be applied for practical prevention.