At present, all hepatitis B vaccines in China are genetically engineered vaccines, which are purified hepatitis B surface antigen. The live hepatitis B virus mainly consists of hepatitis B surface antigen, hepatitis B e antigen and hepatitis B core antigen. The single purified surface antigen is equivalent to the shell of the virus, which will not lead to hepatitis B virus infection in the vaccinated population, and generally will not affect pregnancy. The side effects of hepatitis B vaccine include local reactions and systemic reactions. Local reactions include redness, swelling, itching and hard nodules at the vaccination site, which will disappear automatically in 1-3 days, and may be accompanied by loss of appetite, nausea, abdominal pain and diarrhea, which will disappear after 24 hours. The systemic reaction is fever, as long as there is a temperature above 39°C, antipyretic drugs can be used and will disappear soon. Only severe allergic reactions can affect pregnancy, but they do not delay it for long.