Abstract
Background
Gestational and congenital syphilis remain major public health concerns, particularly in low- and middle-income countries, with substantial impacts on neonatal health. This study estimated the prevalence of gestational syphilis and the birth prevalence of congenital syphilis, identified factors associated with gestational syphilis, and evaluated the association between congenital syphilis and adverse neonatal outcomes in Guarujá, São Paulo, Brazil.Methods
This cross-sectional study was nested within the population-based Guaru-yá Birth Cohort and included 2,217 hospital births from April 2024 to April 2025. Gestational syphilis was defined by reactive treponemal and non-treponemal tests during pregnancy or delivery, considering diagnosis and treatment during the current pregnancy; adequately treated women were not classified as cases. Congenital syphilis was defined according to clinical, laboratory, or epidemiological criteria compatible with vertical transmission. Adjusted Prevalence Ratios (PR) and 95% Confidence Intervals (95% CI) were estimated using Poisson regression with robust variance.Results
Gestational syphilis prevalence was 12.8% (95% CI: 11.4-14.2), and congenital syphilis birth prevalence was 5.8% (95% CI: 4.8-6.8). Higher gestational syphilis prevalence was observed among women with low maternal education (PR = 2.47; 95% CI: 1.43-4.29), living in poorest households (PR = 1.46; 95% CI: 1.07-2.00), who did not cohabit with a partner (PR = 1.83; 95% CI: 1.45-2.31), who smoked during pregnancy (PR = 1.75; 95% CI: 1.35-2.27), and used illicit drug during pregnancy (PR = 1.70; 95% CI: 1.26-2.28). Women aged ≥ 35 years showed lower prevalence of gestational syphilis compared with those aged 20-34 years (PR = 0.67; 95% CI: 0.47-0.97). Congenital syphilis remained independently associated with fetal or neonatal death (PR = 3.25; 95% CI: 1.74-6.07).Conclusions
Gestational syphilis was strongly associated with socioeconomic vulnerability and behavioral factors. Congenital syphilis remained independently associated with fetal or neonatal death, reinforcing the need for early prenatal access, repeated screening, timely maternal and partner treatment, and strengthened surveillance to reduce vertical transmission.