Maternal Ureaplasma Species Colonization and Neonatal Outcomes: A Large Cohort Study on Preterm Birth and Vertical Transmission

Introduction: The impact of maternal Ureaplasma colonization on vertical transmission and its contribution to acute neonatal morbidity remains unclear. Methods: In this retrospective cohort of 1,647 mother-neonate dyads from a Chinese tertiary center (2020–2025), maternal vaginal and neonatal respiratory Ureaplasma colonization was detected via quantitative real-time polymerase chain reaction. We analyzed associations between maternal colonization and perinatal outcomes, and assessed determinants of vertical transmission and whether neonatal colonization independently predicted severe morbidity in Ureaplasma-positive mothers. Results: Maternal Ureaplasma colonization (prevalence 65.9%) significantly increased risks of very preterm birth (16.2% vs. 8.7%), term premature rupture of membranes (9.3% vs. 5.3%), very low birth weight (11.4% vs. 6.9%), neonatal intensive care unit (NICU) admission (58.6% vs. 52.0%), and respiratory distress syndrome (RDS) (10.6% vs. 7.3%). In Ureaplasma-positive mothers, vertical transmission occurred in 20.7% of exposed neonates, was strongly associated with vaginal delivery (25.4% vs. 15.8% for cesarean) and was inversely correlated with gestational age (43.7% at <28 weeks vs. 6.4% at term). Colonized neonates had significantly higher rates of NICU admission (86.7% vs. 51.3%), RDS (16.4% vs. 9.1%), and intrauterine infection/sepsis (35.6% vs. 25.8%). After confounder adjustment, neonatal colonization remained an independent risk factor for severe illness (adjusted odds ratio 3.06, 95% confidence interval 1.55–6.06). Conclusion: Maternal Ureaplasma colonization predisposes to preterm birth and neonatal morbidity. Vertical transmission varies by delivery mode and is the highest with extreme prematurity. Neonatal Ureaplasma colonization independently predicts severe acute morbidity, underscoring the need for targeted risk stratification and intervention in high-risk dyads.