Factors associated with congenital syphilis among women with gestational syphilis in a public health network in Bogotá, Colombia, 2017–2024: A case-control study

Background Congenital syphilis remains a preventable cause of perinatal morbidity and mortality, and its incidence in Colombia remains well above the elimination target. We aimed to identify maternal and prenatal care factors associated with congenital syphilis among women with gestational syphilis attended in a public health network serving socially vulnerable populations in Bogotá, Colombia. Methods We conducted a retrospective case-control study using surveillance and clinical records from the Subred Integrada de Servicios de Salud Sur E.S.E. for pregnancies ending between 2017 and 2024. Cases were neonates with congenital syphilis according to national surveillance criteria; controls were neonates without congenital syphilis born to mothers with gestational syphilis in the same network. Factors associated with congenital syphilis were identified using multivariable logistic regression with backward elimination. Results We included 743 mother–infant pairs (285 cases and 458 controls). Maternal diagnosis after 28 weeks of gestation (adjusted odds ratio 17.75; 95% confidence interval 11.81–26.69), absence of prenatal care compared with eight or more visits (12.74; 5.03–32.25) and reinfection during pregnancy (3.02; 1.73–5.29) were independently associated with congenital syphilis, whereas a documented history of syphilis was associated with lower odds (0.45; 0.25–0.82). The model showed high discrimination (area under the receiver operating characteristic curve 0.860). Migrant status was associated with congenital syphilis in the crude analysis but not after adjustment. Conclusions Congenital syphilis in this setting was associated mainly with late maternal diagnosis and absent prenatal care, conditions that preclude timely benzathine penicillin treatment. Strengthening early prenatal screening, continuity of care and partner management may reduce vertical transmission in socially vulnerable urban populations.