Curbing the Epidemic: Evolving Public Health Practices and Implications of Prenatal Syphilis Screening Patterns in Ontario, Canada

Abstract

Background: Congenital syphilis rates increased significantly between 2018 and 2023 in Ontario, Canada. Timely prenatal syphilis screening is essential for preventing congenital syphilis. We examined the adoption and impact of universal rescreening recommendations on prenatal screening rates and described universal prenatal syphilis screening patterns and factors associated with no or late screening. Methods: First, we surveyed Ontario public health units (PHUs) to identify changes to local prenatal syphilis screening recommendations between 2018 and 2023. Then, using provincial public health laboratory data from nine PHUs for 2019 to 2023, we examined the impact of rescreening adoption on prenatal screening rates, using a difference-in-differences analysis. Next, we described Ontario’s prenatal syphilis screening patterns by conducting a retrospective cohort study with linked provincial administrative health data. Modified Poisson regression was used to assess factors associated with no or late (third trimester or at delivery) initial screening. Results: Twenty-eight of 34 PHUs responded to the survey; by December 2023, 10 PHUs (36%) had recommended universal prenatal syphilis rescreening. In the difference-in-differences analysis, adoption of universal rescreening recommendations was associated with 392 more monthly tests performed per 1,000 pregnancies (95% confidence interval (CI): 205–579), with effect size varying by PHU. Among 551,733 pregnancies included in the retrospective cohort, 507,193 (92%) received any prenatal syphilis screening and 435,176 (79%) received first-trimester screening. Different maternal phenotypes described individuals receiving no or late prenatal syphilis screening. Syphilis screening within one year before conception (adjusted relative risk, 2.11; 95% CI, 2.07–2.15) was associated with receipt of no screening in pregnancy. Younger age at conception (ages 15–19 vs. 30–34) (4.37; 3.62–5.28), recent injection drug use (3.58; 2.95–4.34), and living in the lowest-income neighbourhood (1.51; 1.33–1.72) were associated with being initially screened at delivery. Discussion: During a period of rapidly evolving syphilis epidemiology, we observed sub-optimal and inequitable uptake of universal prenatal syphilis screening. Universal rescreening recommendations increased prenatal syphilis screening rates at the population-level; however, PHU-level variability highlighted the importance of implementation strategies and local contexts. Targeted and coordinated public health interventions are required to improve prenatal syphilis screening coverage and timeliness.