Since the widespread use of the hepatitis B vaccine, great progress has been made in controlling the transmission of the hepatitis B virus in China, and horizontal transmission among newborns has been controlled. Universal vaccination of newborns with hepatitis B vaccine for several years has been able to reduce the rate of surface antigen positivity in preschool children to less than 1% or even 0.5% in some large cities. However, there are still some problems in the mother-to-child transmission of newborns, and how to interrupt the mother-to-child transmission of HBV is an important issue that needs to be addressed urgently. First, the blockage of transmission during delivery: HBIGHBIG injection immediately after birth The timing of the injection is critical and should be given immediately after birth, the sooner the better, especially when the virus in the mother’s blood is large. Mother-to-child transmission is one of the important modes of transmission of HBV and includes four main routes. Currently, giving newborns hepatitis B immunoglobulin (HBIG) + hepatitis B vaccine is a better way to interrupt mother-to-child transmission. The common method is to inject 100-200 IU of HBIG into one deltoid muscle and 10 μg of hepatitis B vaccine into the other deltoid muscle after birth, followed by another 10 μg of hepatitis B vaccine at 1 and 6 months of age. Because the hepatitis B virus enters the newborn mainly during delivery, if HBIG is injected immediately after birth, the HBIG can neutralize the virus as soon as it enters the body. If the injection is late, the virus will have already entered the liver of the newborn and HBIG will no longer be able to work. Therefore, the timing of HBIG injection is critical and should be given immediately after birth, the sooner the better, especially if the virus in the mother’s blood is large. The reference to prescribing injection within 24 h is not appropriate. Second, the blockage of intrauterine transmission: the application of antiviral drugs is more effective maternal injection of HBIG for the prevention of mother-to-child transmission of HBV is not conclusive, and therefore not recommended. For chronic HBV carriers, antiviral drugs are more effective, but their application should be determined by the level of HBV DNA in their blood and the patient’s wishes. For in utero transmission of HBV, there are no uniform diagnostic criteria, and there are four main ones as follows: 1. At birth, HBsAg (+) in the cord blood or peripheral blood of the newborn. The disadvantage of this criterion is that: cord blood is more likely to be contaminated by maternal blood, and peripheral blood is less likely to be contaminated, but there is still the possibility of maternal blood entering the newborn. In other words, the strong contraction of the uterus during delivery may squeeze the mother’s blood into the newborn. In this case, HBIG and hepatitis B vaccine are fully effective when administered to the newborn immediately after birth. Therefore, it is inappropriate to use the infant’s peripheral blood HBsAg (+) at birth as a criterion for intrauterine transmission. 2. At birth, the newborn’s cord blood or peripheral blood HBsAg (+) is still positive on retest 1 month later. This criterion also cannot completely exclude the possibility of maternal blood being mixed during delivery. 3. Newborns who are still HBsAg (+) at 6 months of age after regular HBIG and hepatitis B vaccine prophylaxis after birth. This criterion is more appropriate because the possibility of being infected at birth is ruled out after formal prevention after birth. 4. HBV DNA (+) in the liver tissue of the fetus. This can confirm the diagnosis, but livers of newborns are difficult to obtain, and livers of induced fetuses, although available, can only be used for research applications. The frequency of HBV transmission in utero has been reported differently and varies widely. The timing of intrauterine transmission of HBV is extremely important, as it is related to the timing of interruption. At present, it seems that intrauterine transmission occurs mainly at the end of pregnancy. However, it is also possible, although less likely, in mid- and even early gestation. Yan YP et al. reported the rate of placental HBV infection: 4.2% (1/24) in early pregnancy, 16.7% (1/6) in midterm, and 44.6% (45/101) in late pregnancy; the rate of fetal infection: 1/6 in midterm (induced) and 7.92% (8/101) in neonates. The relationship between placental infection and fetal infection: 6/45 with intrauterine infection in those with placental infection and 2/56 with intrauterine infection in those with uninfected placenta. The gestational age of induced fetuses studied for the presence of HBV DNA in the fetal liver was mostly after 28 weeks. This indicates that fetal infection is mainly through the placenta (placenta is infected first and then infects the fetus), and the rate of infection increases the later the gestation. However, the fetus may also be infected in the middle of pregnancy, and the fetus may also be infected in those whose placenta is not infected. An et al. studied HBV DNA in the liver of fetuses induced by mothers with HBsAg (+) and found that the gestational age was 15 weeks in one case of free replication and 17, 24 & 28 weeks in three cases of integrated type. This indicates that the fetus can be infected from the 15th week of gestation, and the status of the fetus before the 15th week is unknown. This is because all fetuses before 15 weeks are aborted (scraped) fetuses and do not have access to the liver. There are two main methods of interruption of intrauterine transmission: 1. HBIG injection by the mother is generally recommended in the last 3 months of pregnancy (usually starting from the 28th week of gestation), with 200 IU of HBIG injected 3 times a month. After the birth of the newborn baby, HBIG + hepatitis B vaccine prophylaxis is routinely administered. It has even been suggested that HBIG injections in mothers have the potential to reduce the amount of HBV DNA in the serum. In fact, there are many reports of HBIG being ineffective. In conclusion, although there is no conclusive evidence on the effectiveness of HBIG injections in mothers for the prevention of mother-to-child transmission of HBV, this method is not recommended if HBIG injections do not definitively reduce the level of HBV DNA in the mother’s blood (by at least 2log10 copies/ml) or if there is another mechanism. Therefore, clinicians should observe the efficacy of HBIG and also observe the changes in HBV DNA in the mother’s blood before and after the injection or study other mechanisms in order to finally determine whether it is indeed efficacious. 2, the mother applied antiviral drugs antiviral drugs, interferon class has a negative impact on the fetus, so should not be used. Among the nucleoside (acid) analogues, adefovir and entecavir have teratogenic effects on animal fetuses and should not be used. Although lamivudine has adverse effects on animal fetus, a large amount of clinical materials prove that it is safe for human fetus. Tebivudine has no teratogenic effect on animal fetus, and a small amount of clinical material also proves that it is safe for human fetus. Tenofovir has no teratogenic effect on animal fetus, and a large amount of clinical materials also prove that it is safe for human fetus. Therefore, lamivudine, telbivudine and tenofovir can all be used for the interruption of mother-to-child transmission of HBV. Studies have shown that the incidence of neonatal malformations of lamivudine and tenofovir used during pregnancy is not higher than the general incidence of neonatal teratogenicity, so both can be used for the blockade of mother-to-child transmission of HBV. The effectiveness of blockade varies depending on the duration of drug administration and the amount of HBV DNA in the mother’s blood. In conclusion, for chronic HBV carriers, the application and timing of antiviral drugs should be decided according to the level of HBV DNA in their blood on the one hand, for example, those with <104 copies/ml may not be used (for caution, they may also be applied in late pregnancy), and those with very high HBV DNA (>108 copies/ml) must apply lamivudine or telbivudine, and the earlier the application, the better (preferably before the start of pregnancy). On the other hand, the decision should be made according to the patient’s wishes, and for those who want their newborn to be absolutely free of infection, it is best to start before pregnancy and wait until the HBV DNA is negative. On the other hand, the decision should be made according to the patient’s wishes. If the newborn is absolutely free of HBV, it is best to start before pregnancy and wait until the pregnancy is negative for HBV DNA, but transovarian transmission cannot be completely excluded, although this possibility is extremely rare. As to when to discontinue the drug, it may be considered after delivery, but the patient must be closely monitored to prevent deterioration of the disease. For patients with chronic hepatitis B (elevated serum transaminases) requiring treatment, lamivudine or telbivudine is applied at any time as needed. Third, the blockage of transmission after delivery: breastfeeding is safe HBsAg and HBV DNA can be detected in breast milk, but breast milk cannot transmit HBV virus, so breastfeeding is safe. Attention should be paid to breast milk transmission after delivery. HBsAg and HBV DNA can be detected in breast milk, for example, Wong et al. reported that HBsAg could be detected in 72% of breast milk. Shen Jing et al. reported that HBV-DNA was detected in 40 cases (46%) of 87 HBV-M positive maternal colostrums, and there was no one positive case in the control group (P<0.01), but the answer is no whether breast milk can transmit HBV. Long before vaccination, the risk of breastfeeding was also not higher than that of artificial feeders. beasley reported that 92 breastfeeders vs. 55 artificial feeders had 53% vs. 60% HBsAg (+) at 6 months. Hill et al. reported 0% vs. 3% HBsAg (+) at 6 months in 101 breastfed vs. 269 artificially fed infants. All of these data suggest that breastfeeding is safe.