Many patients have the question: Can a father pass hepatitis B to his children? How contagious is it? How to prevent it? 1. Can a father pass hepatitis B to his children? It can be transmitted to children. According to the following: 1) It is true that clinically you can see a father who is hepatitis B positive, a mother who is hepatitis B negative, and a child who is hepatitis B positive. 2) The sperm of a hepatitis B-positive person can indeed carry hepatitis B virus nucleic acid (HBV DNA), which is the most infectious. 3) The sequence of the nucleic acid of the father’s hepatitis B virus (the order of nucleotide arrangement) and the nucleic acid of the child’s hepatitis B virus are basically the same, and even its mutation sites are the same. This is a good indication that the hepatitis B virus of his children is derived from his father’s. 2. How infectious is it? It is not yet known. But it does seem to be much less likely than mother-to-child transmission. Why is this not known? This is because it is very difficult to determine if the transmission is from father to child, and the diagnosis cannot be made solely on the basis of the fact that the father is hepatitis B positive, the mother is hepatitis B negative, and the child is hepatitis B positive. The sequencing of hepatitis B virus nucleic acid is so expensive that hospitals generally do not do it. Therefore, this material is not available yet. 3. How to prevent? If a man with hepatitis B is negative for hepatitis B virus nucleic acid in his blood, he will not infect his child and can go without treatment. If you are currently taking antiviral drugs and are negative for hepatitis B virus nucleic acid, you should switch to telbivudine or tenofovir (lamivudine is also available) and continue to be negative for hepatitis B virus nucleic acid for 1-2 months after which you can also have children. If the hepatitis B virus nucleic acid positive, especially when the titer is high (>105 copies/ml), you should use antiviral drugs (tenbivudine or tenofovir, lamivudine can also be), until after the hepatitis B virus nucleic acid turns negative and then 4 months, if the hepatitis B virus nucleic acid is still negative, then you can have children. This is because the life span of sperm is generally 100 days, so after the hepatitis B virus nucleic acid has turned negative and then used for 4 months, the infected sperm have died out, and the newborn sperm will not be infected again because the hepatitis B virus nucleic acid has been negative. The new sperm will not be infected because the nucleic acid of the hepatitis B virus has been negative. So are these 3 antiviral drugs likely to have a negative effect on sperm? Although there is a lack of direct evidence, it appears that there may be no effect from the use of drugs for mother-to-child transmission. It must be emphasized that normal pregnancies, without any drugs, have a 1-2% teratogenic rate in newborns. Therefore, in case of malformations in the newborn, it cannot be said that they are caused by drugs.