Pregnant women who are positive for hepatitis B virus surface antigen must have their infants routinely vaccinated with hepatitis B virus vaccine and hepatitis B high-valent immunoglobulin at birth, which is currently the most effective method of blocking vertical transmission of hepatitis B virus from mother to child at the time of birth. However, this postnatal interruption is not 100% effective, and intrauterine infection occurs in more than 5% of fetuses when the maternal blood level of hepatitis B virus DNA exceeds 4 times 10 per milliliter. This percentage is not low and should not be ignored. If this 5% of intrauterine infections can also be blocked, it will undoubtedly be a very meaningful event, both for the future new life and for the family. Therefore, the question of antiviral treatment during pregnancy and how to do so is then raised. Chinese physicians have made useful attempts to interrupt intrauterine mother-to-child transmission of hepatitis B virus, leading the way internationally, and the relevant clinical findings have been included in the guidelines for the management of chronic hepatitis B developed by the internationally renowned European Association of Liver Diseases. What is the most important concern for antiviral treatment during pregnancy? Obviously, drug safety is of primary importance. The safety mentioned here has to be considered from two aspects. First, the safety of the fetus. There are three oral anti-hepatitis B virus drugs that are currently recommended for use in pregnant women, namely lamivudine, telbivudine and tenofovir. These three drugs, especially telbivudine and tenofovir, were experimentally proven to be pregnancy class B drugs when they were marketed in the early years. The so-called class B drugs, that is, in animal experiments to confirm that they do not cause fetal malformation, and do not affect fetal development, but can not be extrapolated to humans. Obviously, from the ethical point of view, it is not possible to use pregnant women in clinical trials, so the so-called class A antiviral drugs that are absolutely safe for pregnant women do not exist. However, the safety of these two drugs in humans has been verified due to various reasons, such as “accidental” administration of antiviral drugs by pregnant women, or failure of effective contraception during administration, and refusal of pregnant women and their family members to terminate the pregnancy, or refusal of pregnant women and their family members to terminate the pregnancy even after being advised by doctors. A very convincing comparative study was done to compare the incidence of fetal malformations in women taking tenofovir with the incidence of malformations in the “natural” state, and it was found that there was no difference between the two. At present, it is relatively certain that the three drugs mentioned above are safe for the fetus when taken in the late pregnancy, that is, the last stage of pregnancy (the second trimester). Second, the safety of pregnant women. The main adverse effect of tebivudine is muscle damage, which is manifested by weakness and myalgia within one year of drug use, and whether muscle damage can be detected by laboratory tests. The main laboratory index is phosphocreatine kinase (CK for short), the level of this index reflects the degree of muscle damage. Adverse effects of tenofovir include kidney damage and disorders of calcium and phosphorus metabolism. Fortunately, both CK elevation caused by tenifovir and renal damage caused by tenofovir, etc., one is not high in incidence, and the vast majority can recover after discontinuation of the drug. According to the author’s clinical practice experience, there are not many cases that really lead to serious harm. However, regardless of the incidence of adverse drug reactions, regular monitoring of relevant indicators after treatment is necessary. Once abnormalities are detected, timely treatment under the guidance of a doctor is also necessary.