Factors associated with preterm birth and low birth weight among syphilis-infected pregnant women

To investigate the preterm birth (PTB) and low birth weight (LBW) among syphilis-infected pregnant women and to identify the factors associated with these outcomes. Syphilis-infected pregnant women and their newborns in Changsha City between 2013 and 2023 were investigated. Chi-square trend tests were used to determine trends in the rates of PTB and LBW among syphilis-infected pregnant women. Binary logistic regression models and adjusted odds ratios (AOR) were used to identify factors associated with PTB and LBW among syphilis-infected pregnant women. The overall rates of PTB and LBW among syphilis-infected pregnant women in Changsha City between 2013 and 2023 were 8.79% and 5.23%, respectively. Binary logistic regression analysis showed that factors associated with an increased odds of PTB among syphilis-infected pregnant women included maternal age ≥ 36 years (AOR = 1.43: 95% CI: 1.05–1.93), farmer (AOR = 1.56: 95% CI: 1.03–2.36), housework or unemployment (AOR = 1.56: 95% CI: 1.14–2.14), unmarried/divorced/widowed (AOR = 1.69: 95% CI: 1.09–2.60), and pregnancy-induced hypertension (AOR = 3.79: 95% CI: 1.68–8.54). In contrast, standardized treatment was associated with a reduced odds of PTB (AOR = 0.34: 95% CI: 0.21–0.55). Similarly, factors associated with an increased odds of LBW among syphilis-infected pregnant women included unmarried/divorced/widowed (AOR = 2.33: 95% CI: 1.49–3.65), pregnancy-induced hypertension (AOR = 3.81: 95% CI: 1.44–10.11), non-Treponema pallidum titer at diagnosis ≥ 1:8 (AOR = 1.46: 95% CI: 1.01–2.11), and stillbirth history (AOR = 2.15: 95% CI: 1.04–4.42). Standardized treatment was also was associated with a reduced odds of LBW (AOR = 0.45: 95% CI: 0.26–0.78). In summary, several factors were associated with PTB and LBW among syphilis-infected pregnant women. Our findings hold significant public health implications as some factors are modifiable or avoidable. Interventions such as promoting childbearing at optimal ages, preventing pregnancy-induced hypertension, and improving standardized treatment rates could potentially reduce the rate of PTB and LBW. Not applicable.