The Mortality of Congenital Syphilis

To document the case-fatality rate (CFR) of congenital syphilis diagnosed by molecular tools and rabbit infectivity testing (RIT) of clinical specimens in addition to standard evaluation and to compare that with the CFR using the Centers for Disease Control and Prevention (CDC) surveillance case definition.

Prospective, single site, cohort study of all cases of syphilis among mothers and their infants from 1984 to 2002. The diagnosis of congenital syphilis was determined using IgM immunoblotting, polymerase chain reaction, and RIT of fetal or infant specimens in addition to clinical, laboratory, and radiographic criteria. Data were retrospectively reviewed to ascertain fetal and neonatal mortality.

During the 18-year study, there were 191 cases of congenital syphilis confirmed by abnormalities on clinical, laboratory, or radiographic evaluation and/or positive serum IgM immunoblot, blood polymerase chain reaction, or blood/cerebrospinal fluid RIT. Of the 191 cases, 59 died for a CFR of 31%. Of the 59 deaths, 53 (90%) were stillborn and 6 (10%) died in the neonatal period. The majority (74%, 39/53) of stillbirths occurred in the third trimester. The CDC surveillance case definition correctly identified all infants with congenital syphilis, but the CDC CFR was 10% which underestimated the CFR by more than 300%.

Our findings corroborate the high sensitivity of the CDC surveillance definition for congenital syphilis but highlight its poor estimation of its associated mortality. The CFR among infected progeny of pregnant women with syphilis was 31%, due mostly to demise in the third trimester and as such highlights the need for detection and appropriate treatment of syphilis during pregnancy.