Trends in Syphilis in Pregnant Women in Japan in 2016 and 2022.

Since 2012, the rate of syphilis infection has increased dramatically in high-income countries including Japan. In this study, we examined the rate of syphilis infection among pregnant women and perinatal outcomes in the syphilis-infected pregnancy in 2022 in Japan, and compared the results with those in 2016. We requested 2,005 obstetric institutes to provide information on syphilis infection in pregnant women who delivered in 2022. A total of 1,346 obstetrical facilities responded with valid information. We compared the results with those in our previous study. The prevalence of syphilis-infected pregnant women was 1/1,215. The incidence of preterm delivery, intrauterine fetal demise and congenital syphilis in surviving neonates in the syphilis-infected pregnancy were 9%, 2% and 7%, respectively. The prevalence of syphilis-infected pregnant women has increased significantly, while the incidence of congenital syphilis seems to have decreased clinically.