Background: Syphilis screening during pregnancy helps prevent congenital syphilis. The harms associated with false positive (FP) screens and whether screening leads to correct treatments has not been well determined.
Methods: The population included mothers and infants from 75 056 pregnancies. Using laboratory-based criteria we classified initial positive syphilis screens as FP or true positive (TP) and calculated false discovery rates. For mothers and infants we determined treatments, clinical characteristics, and syphilis classifications.
Results: There were 221 positive screens: 183 FP and 38 TP. The false discovery rate was 0.83 (95% confidence interval [CI], 0.78-0.88). False discovery rates were similar for traditional 0.83 [95% CI, 0.72-0.94] and reverse algorithms 0.83 (95% CI, 0.77-0.88), and for syphilis Immunoglobin (Ig) G 0.79 (95% CI, 0.71-0.86) and total 0.90 (95% CI, 0.82-0.97) assays. FP screens led to treatment in 2 women and 1 infant. Two high-risk women were not rescreened at delivery and were diagnosed after hospital discharge; 1 infant developed congenital syphilis. Among 15 TP women with new syphilis, the diagnosis was before the late third trimester in 14 (93%). In one-half of these women, there was concern for reinfection, treatment failure, inadequate treatment or follow-up care, or late treatment, and their infants did not achieve an optimal syphilis classification.
Conclusions: Syphilis screening identifies maternal syphilis, but limitations include FP screens, which occasionally lead to unnecessary treatment, inconsistent risk-based rescreening, and among TP mothers failure to optimize care to prevent birth of infants at higher risk for congenital syphilis.