Objective   To analyze the characteristics of pregnant women infected with syphilis and the influencing factors of mother to child transmission in Guangdong province, and provide evidence for the development of policies form the elimination of the mother to child transmission.

  Methods   Infected pregnant women who developed fetal transmitted syphilis from January 1, 2014 to February 1, 2021 in Guangdong Province were selected as the case group, and another pregnant women with syphilis infection who did not develop fetal transmitted syphilis were screened as the control group using the same region and year of delivery as matching conditions.

  Results   Multivariate conditional logistic regression analysis showed that compared with pregnant women aged ≤20 years, the risk for mother to child transmission of syphilis was lower in those aged 21−25 years (OR=0.537, 95% CI: 0.341−0.845), 26−30 years (OR=0.43, 95% CI: 0.272−0.679), 31−35 years (OR=0.322, 95% CI: 0.202−0.512) and ≥36 years (OR=0.321, 95% CI: 0.194−0.532); The risk for the mother to child transmission in pregnant women with non-diagnosed syphilis was higher (OR=1.837, 95% CI: 1.352−2.495); Compared with the pregnant women who were diagnosed with syphilis during pregnancy, the pregnant women who were diagnosed with syphilis during labor and after delivery had higher risk of mother to child transmission of syphilis (OR=2.026, 95% CI: 1.472−2.790), (OR=1.951, 95% CI: 1.333−2.856). Compared with the pregnant women receiving treatment in the first trimester, the pregnant women receiving treatment in the second and third trimesters had higher risk of mother to child transmission of syphilis (OR=3.712, 95% CI: 1.977−6.970), (OR=11.531, 95% CI: 6.363−20.894).

  Conclusion   In the elimination of mother to child transmission of syphilis, it is necessary to strengthen the health education about the prevention and treatment of sexually transmitted diseases, such as syphilis, in young pregnant women, and improve their awareness of syphilis prevention. Early detection, diagnosis and treatment of syphilis in pregnancy are essential to reduce mother to child transmission of syphilis. Early screening, diagnosis and treatment of syphilis can effectively reduce the risk of mother to child transmission of syphilis