(273) Trends in risk factors associated with syphilis infection in pregnancy from 2013-2023.

Rates of syphilis infection in pregnancy continue to increase in the United States, despite universal screening and well-defined treatment algorithms. We sought to evaluate the risk factors associated with syphilis infection in pregnancy and changes in these risk factors over a 10-year period at a single tertiary referral center in Alabama.

Study Design:

We performed a retrospective case-control study of all pregnant individuals delivering at our institution from 2013-2023. All patients who received prenatal care at our institution and underwent laboratory testing for syphilis were included. We compared patients with confirmed syphilis (cases – definition in Table) to those without syphilis (controls). Baseline demographics, medical comorbidities, and infectious data (Table) were considered potential risk factors and compared between groups using bivariate analysis. Significant risk factors (p < 0.05) were analyzed via logistic regression to identify independent risk factors. Tests of heterogeneity were computed to analyze the differential effects of risk factors by year.

Results:

During our study period, a total of 40,137 patients were analyzed, of which 114 (0.28%) had confirmed syphilis infection in pregnancy. Pregnant individuals diagnosed with syphilis were more likely to be younger, Black non-Hispanic race, obese, smoke cigarettes, have gonorrhea (GC) or chlamydia (CT) diagnosed during pregnancy, and have public insurance (Table). Of these risk factors, only Black, non-Hispanic race, increasing BMI, cigarette use, and concomitant GC/CT were noted to be independently associated with syphilis infection in multivariable analysis (Table). The only variable to statistically change over time was the increasing association of private insurance with no syphilis infection (p=0.046).

Conclusion: Risk factors associated with syphilis in pregnancy at our institution largely remained stable over the past decade and consistent with known risk factors. Given rising rates of syphilis in pregnancy nationally, new public health strategies are warranted for these known at-risk populations.