(1116) Previous sexually transmitted infection as a predictor for maternal syphilis infection

Syphilis infection in pregnancy and congenital syphilis rates have dramatically increased in recent years. Yet, there is little evidence to guide individualized screening protocols for high-risk populations. Our aim was to determine if a history of a sexually transmitted infection (STI) predicts first-time syphilis infection in pregnancy amid the current rise in congenital syphilis cases.


Study Design:

We performed a retrospective cohort study of pregnancies receiving prenatal care in a multi-center health-system in the southern United States from January 2015 - June 2024. Patients with prior or current syphilis were excluded. Groups were divided based upon STI history: previous STI before pregnancy or at initial prenatal visit vs no STI history. STIs included were laboratory-confirmed chlamydia, gonorrhea, trichomoniasis, or HIV. The primary outcome was a syphilis diagnosis during pregnancy. Secondary outcome was congenital syphilis. Analysis was performed via Student’s t and χ² tests to calculate, p values, odds ratios (OR) with 95 % confidence intervals (CI).


Results:

Among 57 543 eligible pregnancies, 7 144 (12.4 %) had prior STI exposure. Maternal age, parity, insurance status and gestational age at delivery showed statistically significant differences between groups (Table 1). Syphilis was newly identified in 258 pregnancies (0.45 %). Infection occurred in 1.4 % (97) of women with prior STI versus 0.3 % (161) of those without. Thus, an STI history increased the odds of antenatal syphilis (OR 4.3, 95 % CI 3.33–5.53; p < 0.001). Similarly, congenital syphilis frequency were increased, 0.00% vs 0.21% (OR 4.24, 95% CI 2.23-8.05).


Conclusion:

Any history of STI confers a four-fold increase in the risk of syphilis acquisition during pregnancy. Incorporating prior STI history into early prenatal risk assessment could guide screening intervals, partner screening, and other targeted interventions to allow for early detection and treatment to help mitigate the growing burden of congenital syphilis.