Pregnant women who are positive for hepatitis B virus surface antigen must have their infants routinely injected 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 cannot be ignored. If this 5% of intrauterine infections can also be blocked, it will undoubtedly be a very positive thing, 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. Safety here is considered in two ways. First, the safety of the fetus must be considered. There are three oral anti-hepatitis B virus drugs currently recommended for use in pregnant women, namely lamivudine, telbivudine and tenofovir. These three drugs, especially telbivudine and tenofovir, were experimentally proven to be class B drugs in pregnancy 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 pregnancy, or refusal of pregnant women and their family members to terminate pregnancy even after medical advice; some people have even done a very convincing comparative study. The incidence of fetal malformations in women taking tenofovir was compared with the incidence of malformations in the “natural” state, and it was found that there was no difference between the two. It is now relatively certain that the first three drugs are safe for the fetus when taken in late pregnancy, i.e., the last trimester. The next consideration is the safety of the pregnant woman. The main adverse effect of tibivudine is muscle damage, which is manifested by weakness and myalgia less than one year after the administration of the drug, and laboratory tests can reveal whether the muscles are damaged. The main test indicator is creatine phosphokinase (CK), and the level of this test reflects the degree of muscle damage. Therefore, pregnant women need to be monitored regularly for CK during the use of telbivudine. side effects of tenofovir include kidney damage and disorders of calcium and phosphorus metabolism. Fortunately, both CK elevation due to tenifovir and renal damage due to 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 doctors is also a must. The next concern is whether nucleoside analogs are effective in blocking intrauterine transmission of hepatitis B virus? The main answer to verify this question is whether they can effectively inhibit viral replication in the body after administration, that is, whether they can control the amount of virus to less than 4 times 10 in a relatively short period of time. This question is complex and needs to be carefully comprehended by the reader. The regimen recommended by international guidelines is based on a limited number of clinical trials in which antiviral drugs were started in the last trimester of pregnancy. According to this approach, one of the most intuitive questions is: Is it too late to suppress the virus? Yes, it may be “too late” for many pregnant women. Whether it is telbivudine or tenofovir, it is difficult to ensure that the virus is suppressed to less than the fourth power of 10 within three months, especially if the immune activation has not yet occurred, i.e., the transaminases have been normal, and it is even more difficult to ensure that the virus replication is effectively suppressed within a limited period of time, so we cannot avoid this problem. There are two options for adjustment: first, to conceive after effective suppression of the virus in the body; second, to start antiviral therapy early in pregnancy. The author reiterates the word “complexity”. It is difficult to determine whether immune activation of the hepatitis B virus has occurred in women of childbearing age around 25 years. For women with immune activation, i.e., elevated transaminases and immune damage to the liver, the right choice should be immediate antiviral therapy to suppress viral replication and repair liver damage, and conceive after the viral load has reached an undetectable level and transaminases have largely normalized. Without antiviral treatment, there is not only an increased risk of intrauterine infection in the fetus after pregnancy, but also a risk of developing a very severe form of fatty liver disease in pregnancy due to the existing liver damage and the greatly increased burden on the liver after pregnancy. Such lessons (life lessons) are by no means rare! As for “early pregnancy”, how early is it? It should be after the first month of pregnancy, preferably in the second trimester. The 3-month-old embryo is already well tolerated by the drug, but there is also the problem of not being able to effectively suppress the virus in the pregnant woman and thus ensure effective interruption of intrauterine transmission of the hepatitis B virus. To summarize, couples proposing to make a family plan are advised to weigh the pros and cons adequately. You have to find a balance between the following three risks: first, the risk of intrauterine infection without antiviral, second, the risk of severe liver disease in the later stages of pregnancy when the liver is always in the process of being damaged without antiviral, and third, the risk that antiviral therapy and medications may pose to the fetus and the pregnant woman. As for the use of interferon antiviral, it is not the content of this topic to discuss, because those who use interferon may not conceive. In my long-term clinical practice, I have found that about 90% of pregnant women are unwilling to allow the hepatitis B virus to “pass on” to the next generation, preferring to get pregnant after suppressing the replication of the virus, but about 10% of women or their family members (including husbands and both parents) are unwilling to risk the damage caused by the drugs. Until the drug is fully medically proven to be 100% safe, we must make the relevant data and facts known and leave the final decision to the pregnant woman and her family members. But in terms of the risk-benefit ratio, we are increasingly inclined toward early antiviral treatment.