Disparities in Antenatal Care Utilization but Not Treatment Coverage Between Migrant and Local Pregnant Women with Syphilis: A Retrospective Cohort Study in Taizhou, China

Objective To compare demographic characteristics, antenatal care utilization, treatment coverage, and adverse pregnancy outcomes between migrant and local pregnant women with syphilis, and to identify factors associated with non-standardized treatment and adverse outcomes. Methods This retrospective cohort study included 773 syphilis-infected pregnant women registered in the National Prevention of Mother-to-Child Transmission (PMTCT) Management Information System in Taizhou, China, between 2020 and 2025. The cohort comprised 438 migrant women and 335 local women. Demographic characteristics, antenatal care utilization, standardized treatment, and adverse outcomes were compared. Multivariable logistic regression was used to identify factors associated with adverse neonatal outcomes, preterm birth/low birth weight, and non-standardized treatment. Results Migrant women were younger and had lower educational attainment than local women. The proportion aged ≤ 24 years was 30.8% in migrant women versus 16.1% in local women (P < 0.001); 72.1% of migrant women had junior high school education or below versus 43.0% of local women (P < 0.001). Migrant women had a lower rate of first-trimester antenatal registration (72.8% vs. 88.1%, P < 0.001) and a higher proportion of high TRUST titer (≥ 1:8) (16.9% vs. 11.1%, P = 0.030). Standardized treatment rates were similar between groups (78.5% vs. 79.1%, P = 0.846). After adjustment, migrant status was associated with lower odds of adverse neonatal outcome (aOR = 0.59, 95% CI: 0.39–0.89), while late antenatal registration was consistently associated with adverse outcomes.Third-trimester first antenatal visit was associated with higher odds of preterm birth/low birth weight (aOR = 2.96, 95% CI: 1.26–6.96) and non-standardized treatment (aOR = 5.66, 95% CI: 2.78–11.54). Conclusions Migrant pregnant women with syphilis had greater socioeconomic disadvantage and later antenatal registration than local women, but standardized treatment coverage was similar. Late antenatal registration, rather than migrant status itself, was the main modifiable factor associated with non-standardized treatment and preterm birth/low birth weight. The primary actionable target is early antenatal registration, not migrant status per se.