Abstract
BACKGROUND: Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are sexually transmitted infections implicated in preterm birth and neonatal morbidity. Thailand does not routinely screen for CT and NG antenatally. Their prevalence among women with threatened preterm labor (TPL), preterm labor (PTL), and preterm prelabor rupture of membranes (PPROM) remains unclear. METHODS: We conducted a prospective observational cohort study of 330 pregnant women with TPL, PTL, or PPROM at 28 weeks 0 days to 36 weeks 6 days of gestation who delivered at Siriraj Hospital, Bangkok, Thailand, from 2023 to 2025. Cervical and vaginal swabs underwent nucleic acid amplification testing for CT and NG and were assessed for bacterial vaginosis; maternal and neonatal outcomes were examined using logistic regression. RESULTS: CT prevalence was 5.8% and bacterial vaginosis 8.3%; no NG infection was detected. CT was associated with younger maternal age (P < 0.001) and multiple sexual partners (P = 0.028). CT prevalence was highest in PPROM (12.5%), followed by TPL (5.1%) and PTL (4.5%). CT infection showed a nonsignificant trend toward higher intrapartum fever (12.5% vs 3.5%; P = 0.130). Although overall low birth weight rates were similar, CT-positive cases had more very low birth weight infants (< 2000 g: 25.0% vs 10.6%; P = 0.108). Apgar scores and neonatal intensive care unit admission were similar between groups. Bacterial vaginosis was not associated with preterm subtype or maternal or neonatal outcomes. CONCLUSION: Although Chlamydia trachomatis infection was relatively uncommon, it showed a trend toward higher rates of intrapartum fever and very low birth weight (<2000 g) among women with preterm conditions. CT infection was more frequently detected at earlier gestational ages and was most common in women presenting with PPROM. Risk-based CT screening in women presenting with TPL, PTL, or PPROM may facilitate early detection and prevention of infection-related preterm morbidity. TRIAL REGISTRATION: Thai Clinical Trials Registry TCTR20221118005; date of registration: November 16, 2022; date of initial participant enrollment: June 2023.