Why Congenital Syphilis Still Happens: Lessons From 68 New York City Cases, 2010–2016

Congenital syphilis happens when syphilis passes from a pregnant woman to her fetus. It can strike at any stage of the mother’s infection, but is most likely in primary and secondary syphilis, when transmission rates reach up to 100%. Untreated, syphilis in pregnancy can cause miscarriage, stillbirth and early infant death — yet it is preventable by screening and treating during pregnancy.

Nationally, congenital syphilis rose from 9.2 to 23.3 cases per 100,000 live births during 2013–2017, alongside rising syphilis among women of reproductive age. In New York City, primary and secondary syphilis among women aged 15–44 rose 147% during 2015–2016. The city’s health department reviewed every congenital syphilis case from 2010–2016 to find what went wrong.

Most cases were prevented

During 2010–2016, 578 syphilis infections were reported among pregnant women aged 15–44 in New York City. In 510 (88.2%), no congenital syphilis case is known to have resulted — presumably thanks to early screening and treatment. In 68, it did: eight cases per 100,000 live births, a median of eight a year, with a one-year rise to 19 in 2014 that did not last.

Half the 68 mothers were aged 20–29; 53 (77.9%) were non-Hispanic Black or Hispanic; and 31 of 56 (55.4%) with a known country of origin were born outside the United States.

Where prevention broke down

The department counted prenatal care and testing as timely if they came 45 days or more before delivery, allowing time to follow up a positive test and start treatment at least 30 days before birth.

How the 68 pregnancies unfolded. Image from CDC’s report.

• No timely prenatal care — 21 (30.9%). Of these women, 16 (76.2%) had documented obstacles to care, such as substance use, mental health disorders, recent arrival in the United States or unstable housing, and five cited lack of health coverage.
• Care, but no timely test — 4 (5.9%). For two, the cause was an informatics error — for example, syphilis tests left out when a prenatal “lab order set” was programmed into a new ordering system, in two different health systems. One of these women’s infants died shortly after birth.
• Infected after a negative test — 22 (32.4%). These women tested negative on time, then acquired syphilis during pregnancy. 15 had no documented early third-trimester test, though 12 of them had at least one risk marker — living in a high-syphilis or high-poverty neighborhood, chlamydia during pregnancy, or earlier syphilis. One woman seen in an emergency department with syphilis symptoms in her third trimester was not retested until delivery; her infant was stillborn.
• Positive in time — 21 (30.9%). Six were treated too late or not at all — in one case because the department did not know the woman was pregnant, in another because a provider advised delaying treatment. The other 15 started treatment in time but had test results consistent with reinfection or persistent infection near delivery.

The cases themselves

Only two were confirmed cases or stillbirths: one syphilitic stillbirth and one confirmed case in an infant who later died. The other 66 were probable cases, and 45 of those qualified on maternal criteria alone, with few signs of disease; many lacked a full evaluation — 25 had no long-bone X-ray results and 26 no spinal fluid analysis. The surveillance definition deliberately favors catching every possibly infected infant over precision, because tests may not be done and infants may show no symptoms at birth.

What would prevent more

• Screen every pregnant woman at the first prenatal visit, as New York State requires, and retest women at risk at 28–32 weeks and at delivery, as CDC and the U.S. Preventive Services Task Force recommend. Clear local guidance on who counts as high risk would help; some states mandate universal third-trimester screening, which prevented most cases in Florida and Louisiana, though it may not be cost-effective where syphilis is rare.
• Fix the electronic systems: make sure syphilis tests can be ordered, tracked and received electronically, and flagged when results are missing or positive.
• Reach women who miss prenatal care. In 2015, 83.2% of new mothers citywide began prenatal care in the first trimester, helped by insurance open to pregnant women regardless of immigration status through Medicaid and the state marketplace — but women with syphilis may not know of these services, especially those born abroad.

Limits: some registry data were missing or incomplete, and New York City has relatively few congenital syphilis cases and a syphilis epidemic driven largely by men who have sex with men, so the findings may not apply elsewhere.

Sources

Based on Slutsker JS, Hennessy RR, Schillinger JA, "Factors Contributing to Congenital Syphilis Cases — New York City, 2010–2016," MMWR Vol. 67, No. 39, CDC; a work of the United States government in the public domain.