1.The main ways of mother-to-child transmission
There are three main ways
(1) Intrauterine infection: mostly occurs in late pregnancy, due to aging damage to the placenta, the virus in the maternal blood breaks through the placental barrier into the fetal blood circulation.
(2) Infection during delivery: During delivery, newborns are inevitably exposed to maternal blood or secretions containing HBV, which is also the most important way of mother-to-child transmission.
(3) Contact infection: newborns are infected by close contact with patients after birth.
2.How to interrupt mother-to-child transmission
(1) Hepatitis B immune globulin and hepatitis B vaccine combined immune blockade: from the initial simple vaccine blockade to the later combined globulin and vaccine blockade. The current guidelines for the prevention and treatment of chronic hepatitis B in China have clear recommendations on this, specifically by injecting hepatitis B immune globulin (HBIG) as early as possible within 24 hours after birth, preferably within 12 hours, the earlier the better, at a dose of no less than 100 IU, and by vaccinating 10 micrograms of recombinant yeast or 20 micrograms of Chinese hamster oocyte hepatitis B vaccine at different sites (1 and 6 months after the birth of the infant). It is also necessary to revaccinate the hepatitis B vaccine, and it is also recommended to revaccinate HBIG once a month after birth), the success rate of interruption can reach more than 95%. This method is mainly for newborns without considering maternal factors, because some pregnant women are inactive HBsAg carriers and have very low HBVDNA levels in maternal blood, thus, resulting in such a high interruption success rate. The results may be discounted if a refined classification is done according to the maternal HBVDNA level.
(2) Antiviral therapy during pregnancy
The 2009 European Hepatology Society guidelines recommend oral lamivudine (LAV) for pregnant women with HBsAg(+),HBVDNA ≥7th power of 10 IU/ml at the end of pregnancy, and co-immunization measures are still required after the birth of the infant.
Our 2010 consensus guidelines for the prevention and treatment of hepatitis B state that
①Anti-viral therapy should be given as early as possible when pregnant women have elevated ALT and positive HBVDNA, with the aim of preventing hepatitis exacerbation and liver failure, and at the same time, it can reduce vertical transmission from mother to child.
②Pregnant women in the immune tolerance period can, in principle, be treated without antiviral therapy.
③Pregnant women who failed the first combined blockade should be promptly treated with antiviral therapy when they become pregnant again.
④For pregnant women with active hepatitis, it is safer to start antiviral therapy after 3 months of pregnancy.
⑤The drug of antiviral therapy for pregnant women can choose lamivudine, telbivudine or tenofovir.
⑥Pregnant women with normal ALT and HBVDNA greater than 7 times 10 can take oral antiviral drugs in late pregnancy, which can reduce the chance of infection if the virus is suppressed.
(7) The success rate of combined immunoblockade is greater than 90% if the mother’s HBVDNA is less than the 8th power of 10.
(3) Safety of breastfeeding The currently accepted view is that breastfeeding is possible after standardized co-immunization.
3.The controversy that still exists
(1) whether pregnant women in late pregnancy need to inject hepatitis B immunoglobulin Most of the current evidence comes from domestic, but domestic studies are not randomized controlled trials (RCT), lack of sufficient persuasive power, the World Health Organization and China’s Ministry of Health are not such recommendations. The main question is whether such a small dose of HBIG is sufficient to neutralize the virus in pregnant women? Will it lead to the development of an immune escape strain of HBV? If this immune escape strain is spread in the population, it may affect the efficacy of the existing vaccine. Therefore, HBIG is not recommended for pregnant women!
(2) Is it possible for pregnant women to block and reduce mother-to-child transmission by taking antiviral drugs It is now well established that high viral load in pregnant women is a major cause of immune blockade failure. Therefore, attempts have been made to have pregnant women take antiviral drugs prophylactically during the second trimester, but the results reported both domestically and internationally have been mixed.