371 - Impact of County-Level Social Vulnerability on the Incidence of Livebirths Complicated by Syphilis during Pregnancy

Publication Number: 371.5256

Hannah L. Pulido, Valley Children's Healthcare, Fresno, CA, United States; Fredrick Dapaah-Siakwan, Valley Children's Healthcare, Madera, CA, United States

Background: The rate of syphilis in pregnancy increased by 220% between 2016 and 2022 in the United States. The largest increase occurred in mothers with no prenatal care and community conditions such as transportation, language barriers, and cost of care are noted as barriers to prenatal care. We hypothesized that counties with high social vulnerability index would be associated with a higher incidence of livebirths complicated by syphilis during the pregnancy (LBSyp). The SVI measures social determinants of health in US counties based on 16 social attributes (Figure 1) and has been used to study the impact of social vulnerability on multiple health outcomes.

Objective: To evaluate the impact of county-level SVI on the incidence of LBSyp in the US from 2018-2022.

Design/Methods: We linked the rate of county-level LBSyp for 2018-2022 obtained from the and the 2022 county-level SVI data from the Agency for Toxic Substances and Disease Registry. Counties with < 100,000 population or < 10 cases were excluded per CDC guidelines. We calculated scores for overall SVI and its 4 sub-themes (i.e., socioeconomic status; household composition and disability; minority status and language; and housing type and transportation) (Figure 1). Scores were presented as percentile rankings by county, and further classified as quartiles on the basis of their distribution among all US counties (1st [least vulnerable] = 0 to 0.25; 4th [most vulnerable = 0.75 to 1.00]). Incidence rates of LBSyp per 100,000 livebirths and 95% confidence intervals (CIs) were estimated for the overall population and stratified by SVI sub-themes and SVI quartiles. A negative impact by SVI was characterized by a higher incidence within SVI-Q4 compared with SVI-Q1 and nonoverlapping CIs.

Results: Among 16 million live births in 281 counties, 25,012 were complicated by syphilis during pregnancy. The rate of LBSyp increased in a stepwise manner from SVI-Q1 to SVI-Q4 (Table 1) for the overall SVI and for each of the four sub-themes. For overall SVI, SVI-Q4 quartile had a significantly higher rate of livebirths complicated by syphilis during the pregnancy (3.7) and accounted for 3 excess cases per 100,000 livebirths compared to SVI-Q1 (0.7). Similarly, when compared to SVI-Q1, SVI-Q4 had an excess incidence rate of LBSyp for each of the SVI sub-themes.

Conclusion(s): Counties with higher social vulnerability index were associated with a higher rate of LBSyp. These findings suggest the need for increased attention and allocation of resources to counties with high to support syphilis prevention efforts.

Figure 1
The CDC/ATSDR Social Vulnerability Index (SVI) and the 16 U.S. census variables from the 5-year American Community Survey used to compute the SVI

Table 1
Incidence per 100,000 livebirths and their corresponding 95% Cis and rate difference for livebirths complicated by syphilis during pregnancy in quartiles based on SVI.