The causative agent of syphilis is syphilis spirochete, discovered in 1905, is small and slender spiral microorganism, 5~20μm long, average length 6~10μm, thickness <0.2μm, with 6~12 spirals. Because syphilis spirochetes are transparent and not easily stained, they are also called pale spirochetes. Syphilis spirochetes do not survive easily outside the body, boiling, disinfection, drying and general disinfectants can easily kill them, and their morphology and toxicity can still be preserved at low temperatures for several years. The role of the cellular immune response in the immunopathology of syphilis is unclear, and in the humoral immune response, spirochetes invade the body to produce a variety of antibodies. After pregnancy in syphilis patients, the fetus is infected with syphilis spirochetes through the blood route in the mother. Because the mode of infection is different from acquired syphilis and the fetus has a different constitution than adults, the symptoms are different from acquired syphilis, and no hard chancre occurs, often with more severe visceral damage, which has a great impact on the health of the affected child and a high morbidity and mortality rate. There is no definite conclusion on whether or not to expel syphilis treatment after pregnancy in patients with serum fixed syphilis, but because syphilis spirochetes may still be present in the body of patients with serum fixed syphilis, women should go to the hospital for syphilis RPR testing in advance before planning pregnancy, especially for some risk groups, such as those who have had syphilis infection, those who have had unclean sex, those whose sexual partners have syphilis infection and those who have a history of blood transfusion. In order to detect and diagnose early and treat early, for pregnant women who have not made pre-pregnancy check-ups, obstetricians must screen them for syphilis RPR in early pregnancy or during the first maternity check-up, and for high-risk pregnant women with negative RPR, they should be checked again before delivery to prevent missed diagnosis. Once syphilis is detected during pregnancy, regular treatment should be administered according to the course of treatment. Serofixed patients should preferably undergo a thorough physical examination before pregnancy to exclude possible underlying lesions such as neurosyphilis, cardiovascular syphilis, and bone syphilis, or else regular de-syphilis treatment is recommended to be repeated after pregnancy.