Congenital syphilis: trends in mortality and morbidity in the United States, 1999 through 2013

Abstract

Background: Congenital syphilis (CS) results when an infected pregnant mother transmits syphilis to her unborn child prior to or at delivery. The severity of infection can range from a delivery at term without signs of infection to stillbirth or death after delivery.

Objective: We sought to describe CS morbidity and mortality during 1999 through 2013.

Study design: National CS case data reported to Centers for Disease Control and Prevention during 1999 through 2013 were analyzed. Cases were classified as dead (stillbirths and deaths up to 12 months after delivery), morbid (cases with strong [physical, radiographic, and/or nonserologic laboratory] evidence of CS), and nonmorbid (cases with a normal physical examination reported, without strong evidence of infection). Annual rates of these cases were calculated. Cases were compared using selected maternal and infant criteria.

Results: During 1999 through 2013, 6383 cases of CS were reported: 6.5% dead, 33.6% morbid, 53.9% nonmorbid, and 5.9% unknown morbidity; 81.8% of dead cases were stillbirths. Rates of dead, morbid, and nonmorbid cases all decreased over this time period, but the overall proportions that were dead or morbid cases did not significantly change. The overall case fatality ratio during 1999 through 2013 was 6.5%. Among cases of CS, maternal race/ethnicity was not associated with increased morbidity or death, although most cases (83%) occurred among black or Hispanic mothers. No or inadequate treatment for maternal syphilis, <10 prenatal visits, and maternal nontreponemal titer ≥1:8 increased the likelihood of a dead case; risk of a dead case increased with maternal nontreponemal titer (χ(2) for trend P < .001). Infants with CS born alive at <28 weeks' gestation (relative risk, 107.4; P < .001) or born weighing <1500 g (relative risk, 43.9; P < .001) were at greatly increased risk of death.

Conclusion: CS remains an important preventable cause of perinatal morbidity and mortality, with comparable case fatality ratios during 1999 through 2013 (6.5%) and 1992 through 1998 (6.4%). Detection and treatment of syphilis early during pregnancy remain crucial to reducing CS morbidity and mortality.

Keywords: congenital syphilis; infant mortality; prenatal care; sexually transmitted disease surveillance; stillbirth.

FIGURE 1. Rates of congenital syphilis (CS), by severity of disease–United States, 1999 through 2013

In descending order of severity: stillborn infants and infants who died up to 12 months after birth (dead); infants with strong evidence of syphilis, based on testing indicative of syphilis, physical signs or symptoms of syphilis, and/or (in mother untreated or inadequately treated for syphilis) elevated cerebrospinal fluid (CSF) white blood cell count or CSF protein concentration absent other causes (see “Materials and Methods”) (morbid); infants lacking evidence of infection present in morbid cases, with normal physical examination reported (nonmorbid); and infants lacking evidence of infection present in morbid cases, without normal physical examination reported (unknown). Overall, rates of dead, morbid, and nonmorbid cases of CS all declined during 1999 through 2013. While rate of dead cases declined slightly and very gradually throughout 1999 through 2013, rates of morbid and nonmorbid cases declined most during 1999 through 2005.

FIGURE 2. Rates of dead cases of congenital syphilis (CS), by race/ethnicity of mother–United States, 1999 through 2013

Because cases of CS born to non-Hispanic black (black), non-Hispanic white (white), and Hispanic mothers accounted for 94% of reported cases of CS, this chart focuses on these 3 races/ethnicities. During 1999 through 2013, rates of dead cases of CS decreased among black mothers and Hispanic mothers, but remained relatively unchanged among white mothers. In 2013, rate of dead cases of CS among black mothers and Hispanic mothers was 7.5 and 4.5 times rate among white mothers, respectively.