Prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, and Bacterial Vaginosis and Their Association with Maternal and Neonatal Outcomes in Women Presenting with Threatened Preterm Labor, Preterm Labor, and Preterm Prelabor Rupture of Membranes

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. Plain Language Summary: This study looked at how common certain infections are in pregnant women who experience early labor or early rupture of the membranes before birth. These infections can increase the risk of complications for both mothers and babies, but they are often not tested for during routine pregnancy care in Thailand. Researchers studied 330 pregnant women between 28 and 36 weeks of pregnancy at Siriraj Hospital in Bangkok. They tested for Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and bacterial vaginosis (BV). They also followed mothers and babies to understand how these infections may affect health outcomes around the time of birth. The results showed that CT was found in about 6% of women and BV in about 8%, while NG was not detected. CT infection occurred more often in younger women and in those who had early rupture of the membranes. Although serious complications were uncommon, women with CT infection showed trends toward higher rates of fever during labor and very low birth weight babies. Overall, this study shows that these infections are not common, but they may still play a role in some early birth complications. Testing women who show signs of early labor or membrane rupture may help doctors find and treat infections earlier and support safer outcomes for mothers and babies. Keywords: chlamydia trachomatis , nucleic acid amplification test, PPROM, pregnancy, preterm labor, sexually transmitted infection, threatened preterm labor