Background: Congenital syphilis (CS) remains a significant public health issue in Brazil despite universal access to testing and treatment. Untreated partners can enable maternal reinfection, yet its national coverage and determinants are unclear. This study aimed to quantify the coverage of adequate partner treatment among CS cases and to identify sociodemographic and care-related factors associated with it.

Methods: Repeated cross-sectional study of all CS notifications in Brazil's Notifiable Diseases Information System (SINAN), 2007-2023. Records with missing information on partner treatment status were excluded from main analysis. The outcome was documented adequate partner treatment in SINAN. Multivariable logistic regression estimated adjusted odds ratios (aORs) and 95% CIs.

Findings: From 2007 to 2023, 297,062 CS cases were reported. CS notification rates increased from 1·9 to 9·6 per 1000 live births in the period. Coverage of adequate partner treatment rose modestly from 20% (n = 809) in 2007 to 27·7% (n = 4864) in 2023. Median maternal age was 23 years (IQR 20-28). Most cases occurred among Mixed (126,434; 57·9%), White (54,465; 24·9%), and Black women (20,534; 9·4%). Higher maternal education (aOR 2·41, 95% CI 2·35-2·48) and receipt of prenatal care (aOR 2·64, 95% CI 2·56-2·73) were associated with partner treatment, whereas odds were lower among Black (aOR 0·85, 95% CI 0·82-0·89) and Mixed women (aOR 0·81, 95% CI 0·79-0·84) and in the North region.

Interpretation: Documented adequate partner treatment remained low and inequitable across race, education, and region amid rising CS rates. Because cases missing partner-treatment status had poorer care engagement, real estimates are likely worse. Strengthening partner management within antenatal care, ensuring benzathine penicillin availability and improving surveillance capture of partner-treatment indicators are essential to advance EMTCT goals in Brazil.