The concept of antiviral therapy for chronic hepatitis B is becoming more and more deeply rooted. According to the natural history of chronic HBV infection, women of childbearing age with chronic HBV infection before the age of 35 are either in the immune tolerance period or in the viral clearance period of chronic hepatitis, and the majority of these infected patients are serum HBV DNA positive. For the general population, immune tolerance does not require treatment, but for pregnant HBV DNA-positive women, antiviral therapy is again needed to reduce the probability of mother-to-child transmission of HBV, but there is a need to consider the effect of antiviral drugs on the fetus, therefore, antiviral therapy for women in pregnancy is different from the general population. Anti-HBV therapy for pregnant women with HBV infection involves not only the pregnant woman herself, but also the fetus and the interruption of mother-to-child transmission of HBV, which is one of the most important means of reducing chronic HBV infection in China. However, because of the special characteristics of pregnant women, including the immune environment of pregnant women, the impact of HBV infection on pregnant women and fetuses, the selection of treatment cases, the purpose of treatment, the start time and termination of treatment, and the selection of therapeutic drugs, the principles of their antiviral treatment differ greatly from those of chronic hepatitis B. Effect of pregnancy on HBV and HBV on pregnancy: Since pregnant women have high levels of adrenocorticotropic hormone in their blood and therefore may have increased viremia, pregnant women are often associated with increased numbers and activity of regulatory T cells, which also leads to an inadequate immune response to HBV, whereas animal experiments have confirmed that estradiol in the blood of pregnant women can nevertheless reduce viral replication, and therefore no viremia has been observed during pregnancy Naturally significant changes in viremia were not observed during pregnancy. Probably based on these factors, most pregnant women can maintain stable viral load and liver function, but some pregnant women can have a tendency to have elevated ALT in the second trimester and after delivery, and some pregnant women can also have a sudden onset of hepatitis (flare) with or without serological conversion to HBeAg within 6 months after delivery, presumably associated with a rapid decrease in cortisol levels after delivery, which to some extent corresponds to steroid withdrawal. This is presumed to be associated with a rapid decrease in cortisol levels after delivery, and to some extent corresponds to the serologic switch caused by steroid withdrawal. In studies of HBV infection on pregnancy, the effect of chronic HBV infection on pregnancy is unclear, and a large study confirmed that there were no differences in birth weight, incidence of preterm birth, neonatal jaundice, congenital anomalies, and perinatal mortality between HBsAg-positive mothers and HBsAg controls in the chronic HBV infection group compared to HBsAg-negative controls on gestation. However, some studies have shown that chronic HBV infection is associated with gestational diabetes and bleeding before delivery. The occurrence of acute HBV infection during pregnancy must be distinguished from other causes of acute liver disease. There is no evidence that acute HBV infection during pregnancy increases maternal mortality or causes fetal malformations. However, low fetal weight and preterm delivery have been reported, in addition to the fact that acute HBV infection in early pregnancy can cause 10% of perinatal infections. The purpose and target selection of antiviral therapy in pregnancy: antiviral therapy in pregnancy has two indications, one is to treat the mother’s chronic hepatitis, and the other is to prevent mother-to-child transmission of HBV. Due to the elevated corticosteroids and increased number and activity of regulatory T cells in the blood of pregnant women during pregnancy, even if there is activity of chronic hepatitis B, the vast majority of them are milder and deterioration of hepatitis rarely occurs. Among 1278 pregnant women delivered from January 1 to December 31, 2009 at Beijing Ditan Hospital, 80.0% had normal ALT levels, 9.9% had 40-80 U/L, 5.6% had 2-5 times the normal upper line, and 3.5% had 5-10 times the normal upper line 1.7% were greater than 10 times the normal upper line. Due to the nature of the immune environment of pregnant women, even if antiviral therapy is administered, good results (disappearance of HbeAg and serological conversion) cannot be achieved during pregnancy, therefore, as far as the treatment of chronic hepatitis B in pregnant women is concerned, antiviral therapy is generally not administered. In addition to this, the currently used antiviral drugs including interferon, lamivudine, entecavir and adefovir are classified as Class C drugs by the FDA, while telbivudine is classified as Class B only after animal studies, and tenofovir has not been tested in large scale trials in pregnant women and may still be harmful to the fetus, therefore, in general, full antiviral therapy is not administered to pregnant women to minimize fetal exposure to therapeutic drugs. The risk of fetal exposure to therapeutic agents is therefore not usually treated. However, in a small number of patients with deteriorating liver function or even liver failure due to chronic HBV infection during pregnancy, antiviral therapy is required to prevent further deterioration and to improve the success rate of resuscitation in pregnant women with liver failure. Current antiviral treatment during pregnancy is mainly aimed at preventing mother-to-child transmission of HBV, and numerous studies have shown that mother-to-child transmission of HBV occurs mainly in the perinatal period and is associated with the level of HBV DNA in the mother’s blood. Since China is an area with high prevalence of chronic HBV infection, more pregnant women than in Europe and the United States need antiviral treatment to prevent mother-to-child transmission of HBV. Among pregnant women who gave birth and had their HBV DNA checked from January 1 to December 31, 2009 at Beijing Ditan Hospital, 61.7% (773/1252) had HBVDNA levels greater than 1.0×105 copies/mL, 15.1% had 5.0×102-1.0×105 copies/mL, and only 23.2% had less than 5.0×102 copies/mL (negative). The results of a research project supported by the Capital Medical Development Fund, which was in charge of Ditan Hospital, showed that the cumulative positive rate of HbsAg in newborns at 12 months after vaccination was as high as 13.8% (12/87) in people with high viral load, even if 200 IU of HbIg was injected within 2 hours of birth and 10 micrograms of hepatitis B vaccine was administered three times in the regular procedure (0,1,6), while Lamivudine administration (starting at 28-32 weeks of gestation and continuing until delivery) reduced the probability to 7.7% (3/39), while the cumulative HbsAg positivity in the 12th month after HBIG and hepatitis B vaccination in infants born to HBV DNA-negative pregnant women was only 2.3% (1/43). Other studies have concluded that lamivudine use reduces the probability of mother-to-child transmission of HBV. Since HBV DNA levels in pregnant women are significantly associated with mother-to-child transmission, antiviral therapy is required for most pregnant women with high HBV DNA loads as a means of reducing and preventing mother-to-child transmission, depending on the status of HBV DNA levels in pregnant women in China. Antiviral therapy can be administered to reduce the risk of mother-to-child transmission of HBV after adequate communication with the patient about the purpose and possible risks of antiviral therapy, while antiviral therapy is also recommended for patients who are HBV DNA positive but below the above values, if mother-to-child transmission of HBV has occurred in their previously born newborns. For HBV DNA-negative pregnant women, there is no evidence that antiviral therapy contributes to the interruption of mother-to-child transmission of HBV. Drug selection and timing of treatment initiation: Although interferon, lamivudine, adefovir, entecavir, tipifovir, and tenofovir are all effective and safe for antiviral treatment of chronic hepatitis B, the main consideration for treatment of pregnant women is their effect on the fetus. Therefore, it is important to use drugs that have little effect on the fetus and to minimize the period of fetal exposure to the drugs. Among the current antiviral drugs for chronic hepatitis B, lamivudine, adefovir, entecavir and interferon are all classified as Class C by the FDA, and tenbivudine and tenofovir are classified as Class B drugs, but tenbivudine has only been observed for its teratogenic and developmental effects in animal studies, and there is only one report on tenofovir for antiviral prevention of mother-to-child transmission of HBV in pregnant women, and in the current prevention of mother-to-child transmission of HBV Lamivudine is used in the vast majority of cases in antiviral therapy, and there are only reports on the safety of lamivudine use in pregnant women. Studies have shown that lamivudine is safe for use in the second trimester of pregnancy. Because of its rapid and effective inhibition of HBV replication, lamivudine is currently recommended for use starting in the second trimester of pregnancy (28-32 weeks of gestation), and for good responders 3 months of treatment is sufficient to reduce the virus to a low level at the time of delivery, achieving a reduced risk of mother-to-child transmission of HBV. Currently, antiviral for the prevention of mother-to-child transmission of HBV is not advocated for the entire course of medication for four reasons: 1) to minimize exposure to any potentially harmful drugs before fetal development and maturity; 2) because mother-to-child transmission of HBV occurs mainly in the perinatal period, it is sufficient to reduce the level of HBV DNA in the blood of pregnant women to a certain level before delivery; 3) because of the specificity of the immune environment of pregnant women in pregnancy, even the entire course of (3) Due to the specificity of the immune environment of pregnant women in pregnancy, even if the whole course of antiviral treatment is administered, it may not be possible to achieve serological conversion of HBeAg, but there is a possibility that long-term application of lamivudine may lead to viral mutation, resulting in antiviral failure. In the case of women with unplanned pregnancy while taking nucleoside analogue antiviral drugs, they should be informed of the possible effects of continuing the drug on the fetus, the possible hepatitis activity and the possibility of liver function deterioration if they stop taking the drug, and the patient should decide whether to continue the drug or discontinue the treatment. The results of a cohort study including 38 patients with chronic HBV infection who became pregnant while taking lamivudine and chose to continue treatment showed that 36 patients who continued the drug had no pregnancy complications, fetal injury, or mother-to-child transmission, while the two patients who chose to discontinue the drug both developed hepatitis activity within 6 months of discontinuation. The number of cases is too small to demonstrate the absolute safety of the full course of drug use. However, another perspective seems to suggest that in clinical practice, it seems safer to switch the original drug to lamivudine in case of unplanned pregnancy while taking other antiviral drugs. In contrast, pregnant women with progressive liver disease should be treated with full antiviral therapy and continued after the end of pregnancy. When to stop treatment: Since most pregnant women are in the immune tolerance period or have normal ALT during pregnancy, there is no need to continue long-term antiviral therapy after the end of pregnancy in these groups. However, because of the rapid decline in cortisol levels in the months following the end of pregnancy, some individuals can experience withdrawal of cortisol-like ALT activity; therefore, for greater safety, lamivudine is not discontinued immediately; rather, it is best to maintain treatment for 2 to 3 months and follow up after discontinuation of therapy. In contrast, for patients with chronic hepatitis B, antiviral therapy is administered according to the principles of antiviral management of chronic hepatitis B after the end of labor. In conclusion, the main purpose of antiviral treatment in pregnant women is to carry out prevention of mother-to-child transmission of HBV. In pregnant women with high HBV DNA levels, antiviral treatment with oral lamivudine is administered in the second trimester of pregnancy after adequate communication with the pregnant woman to inform her of the purpose and possible risks of antiviral treatment.