Background::So far, there is a paucity of real-world data on the syphilis serological responses to the first-line treatment during pregnancy, and there is no relevant study on the necessity of anti-syphilis treatment during pregnancy for those patients who have been treated for syphilis before pregnancy for the prevention of mother-to-child transmission, which might provide valuable insight into treatment effectiveness and optimal management of pregnant women with syphilis.Methods::A retrospective study on 10 years of real-world data was performed for accumulative 410 Chinese pregnant women with syphilis. The descriptive statistics were conducted in the study, and toluidine red unheated serum test (TRUST) titer responses to penicillin treatment in syphilis-infected pregnant women, and the associations with congenital syphilis were investigated. We divided the patients into two groups according to the history of anti-syphilis treatment before pregnancy (patients diagnosed with syphilis who had received anti-syphilis treatment before pregnancy, and patients screened and diagnosed with syphilis during pregnancy who had no previous history of anti-syphilis treatment).Results::The rate of congenital syphilis in this study was 6.2% (25/406). There was no significant difference in the rate of congenital syphilis between patients who received anti-syphilis treatment before pregnancy and those who did not. Secondary syphilis and high baseline serum TRUST titer (≥1:8) in pregnant women were independent risk factors for congenital syphilis.Conclusions::For the prevention of congenital syphilis, anti-syphilis treatment during pregnancy for syphilis seropositive pregnant women is needed, regardless of whether the patient has received anti-syphilis treatment before pregnancy, especially for those patients with secondary syphilis or high baseline serum TRUST titer, thus, timely surveillance, early diagnosis to timely treatment, and close syphilis reexamination during posttreatment follow-up, may help to reduce the above-mentioned risk factors for congenital syphilis.