How does mother-to-child transmission occur? There are three ways of transmission from mother to child: 1. Intrauterine transmission. 2. Transmission during labor and delivery, which mainly means that the newborn is infected during labor and delivery. 3. Transmission during close contact between mother and child in daily life after birth. If the child has developed surface antibodies after immunization, he or she will not be infected. Can intrauterine transmission be blocked? The incidence of intrauterine transmission is not low in domestic studies of aborted embryos, but a small number of viral infections may be cleared up, and about 5% may become chronic carriers of the virus after birth. How intrauterine transmission occurs is not fully understood, and one possibility is that a very small dislocating injury occurs between the uterus and the placenta. It turns out that the fetus is attached in the uterus by an umbilical cord blood vessel to the placenta, which fits snugly against the inside surface of the mother’s uterus. Both the placenta and the uterine wall are richly vascularized, but not connected. Nutrients in the mother’s blood are able to diffuse from the mother’s blood vessels to the placenta and are then absorbed into the umbilical cord blood to supply the fetus. Viruses are insoluble particulate matter with large molecules that cannot diffuse, and cannot travel from mom’s blood vessels to those of the fetus. If, very by chance, mom falls or gets some kind of violent bump, there is a very small misalignment of the uterus and placenta, a very small rupture of a microscopic blood vessel. All it takes is for a very small amount of the mom’s blood to get into the placenta, and intrauterine transmission of the hepatitis B virus occurs. As long as there is no strenuous exercise during pregnancy, normal activities (including sex) should not spread. How can a pregnant woman with very high levels of the virus block transmission to her newborn? Newborns become infected by contact with their mothers’ blood-carrying fluids during labor and delivery, and many studies have shown that the rate of mother-to-child transmission correlates with the level of virus in the maternal serum at the time of delivery. Chronic hepatitis B virus carriage in pregnant women with HBV DNA ≥7th percentile is associated with more than 20% immunization failure, even with standardized and adequate neonatal immunization. In recent years, a preventive method has been gradually developed: it is possible for mothers to take lamivudine or tibivudine for 2 months beginning at 32 weeks’ gestation, and serum viral levels can generally be reduced by 1 to 2 times the HBV DNA level, with the goal of interrupting mother-to-child transmission in pregnant women with very high levels of the virus during labor and delivery and decreasing the incidence of infection in these newborns. Can intrauterine transmission be blocked by taking the medication in this way? No. This is not possible because: (1) intrauterine transmission can occur throughout the entire pregnancy and the medication is only for the last 2 months; (2) the medication only reduces the level of the virus, but if it is reduced to the 5th power, it can still be transmitted if there is a small misalignment of the placenta. What is the effect on the mother with high viral level? The mother’s liver function is normal, is not an indication for antiviral treatment, and can’t get rid of the “triple sun”, and the virus level is difficult to drop below the 5th power, and will return to the original level soon after stopping the drug, so it is only to temporarily reduce the serum virus level of pregnant women at the time of delivery, and can’t treat the chronic hepatitis B carriage of pregnant women, as we all know: There is currently no cure for chronic hepatitis B carriage. So, is it harmful to the mom? Can the virus rebound and hepatitis occur? Starting lamivudine or tibivudine at 32 weeks of pregnancy is only 2 months, which is a very short period of time, and in general, the chances of the virus rebounding and developing hepatitis after stopping the medication should be very low. However, there is a point to add. Pregnant women who are chronic hepatitis B carriers have a similar chance of developing hepatitis during pregnancy as nonpregnant carriers, but there are quite a few cases of postdelivery onset due to exertion and changes in intra-abdominal pressure, and you need to get your liver function checked at the end of the first month. Can all nucleoside analogs be used? The use of lamivudine as a prophylactic measure to block mother-to-child transmission during the 32nd week of pregnancy in pregnant women with very high levels of chronic hepatitis B carriage has been reported both at home and abroad, and has been used in a number of hospitals in China for many years and is considered to be safe and effective. The teratogenicity of lamivudine and tibivudine to the fetus is certified by the FDA as a class B drug, which is safer than class C (adefovir and entecavir), but it is not a class A drug, and it cannot be considered absolutely safe. Tibivudine effect is stronger than lamivudine, if the expected possibility of preterm labor, pregnant women taking medication less than 8 weeks to use tibivudine is better; lamivudine for 32 weeks pregnant women already have more clinical applications, more assured. Is it useful to give hepatitis B immunoglobulin to pregnant women? In the past, many hospitals in China gave mother-to-child interruption measures by injecting hepatitis B immunoglobulin to pregnant women in the 7th, 8th and 9th trimesters. There have been reports in China, one of which was published in a Chinese-run English journal, but they are not very convincing. Take liver transplantation as an illustration for everyone to understand. Liver transplant recipients have low serum viral levels, generally in the 10th power, at the time of removal of the diseased liver, the standardized need to be infused with hepatitis B immunoglobulin 10,000 units, and every 2 weeks thereafter to be infused with 2,000 units. Look at the “triple positive” carrying mothers, serum virus levels thousands of times more than patients receiving liver transplants, and the infected liver is still constantly replicating a large number of viruses, injection of 200 units of globulin 3 times, even to the virus “scratching” is not enough, how can it be useful? How can it be useful?