Serologic Screening for Syphilis at Delivery: Mother or Infant?

Abstract

Congenital syphilis remains a preventable cause of fetal/neonatal morbidity and mortality. The re-emergence of congenital syphilis (CS) in the U.S. has reinforced the need for optimal screening methods in mothers and infants. The Centers for Disease Control and Prevention (CDC) recommends that all pregnant women be screened for syphilis at the first prenatal visit and, in high-risk areas, at 28 weeks and delivery. Some health care professionals may opt for screening the newborn rather than the mother at delivery. The reliability of such a strategy for identification of syphilis-exposed neonates remains uncertain. To determine whether serologic screening for syphilis at delivery is best performed on the mother or infant for optimal identification of infants at risk for CS. We conducted a retrospective study of infants born to mothers with reactive serologic tests for syphilis from January 1, 2002 to December 31, 2024 who were referred to the NEO-ID Clinic at Nationwide Children’s Hospital, Columbus, OH. Pertinent maternal and infant demographic, clinical, and laboratory data were obtained from electronic health records and in consultation with Columbus Public Health. The results of serologic tests for syphilis among mother-infant dyads at delivery were compared. Among 513 mother–infant dyads, 170 (33%) infants of 168 mothers had a nonreactive RPR test at birth despite the mother having a reactive RPR test at delivery. Most mothers (112/168, 67%) had syphilis of unknown duration. The median (IQR) maternal RPR titer was 1:4 (1:2–1:16). Of the 168 mothers, 26% (n=44) had untreated syphilis at delivery. Of the 170 infants, none had physical examination findings consistent with congenital syphilis, and 54% (n=92) of them received treatment with a single intramuscular dose of benzathine penicillin G per CDC recommendations. Reliance on serologic screening of newborns for syphilis exposure during gestation risks missing a substantial proportion of infants at risk for CS, particularly when maternal RPR titers are low. Serologic testing of mothers and not infants at delivery is recommended for optimal identification and management of at-risk newborns and must be prioritized for CS prevention. (Supported by PIDS SUMMERS Research Grant to SBC)