Trends and Determinants of Preterm Births

Objective Preterm birth remains a leading cause of perinatal morbidity and mortality. This study aimed to retrospectively analyze the trends in preterm birth rates and investigate key maternal and fetal determinants at the Cantonal Hospital Zenica, a secondary referral center, over a five-year period (2020-2024). Methods A retrospective, descriptive-analytical study was conducted that included all preterm deliveries (<37 gestational weeks) at the Department of Gynecology and Obstetrics. Data were collected from official delivery registries. Statistical analysis included linear regression for trends, chi-square tests for categorical variables, and Spearman’s correlation to assess associations between maternal parity, comorbidities (hypertension, obesity, thyroid disorders), mode of delivery, premature rupture of membranes (PROM), and neonatal outcomes (Apgar scores, hospitalization length, and neonatal intensive care unit (NICU) transfer). Results Out of 11,117 total deliveries, 423 (3.80%) were preterm. The incidence remained stable across the study period. Multiparous women accounted for 53.19% of cases. The most prevalent comorbidities were obesity (27.4%) and hypertensive disorders (16.1%). A significant association was found between hypertensive disorders and delivery by cesarean section (73.53%; p<0.005), whereas these mothers had a significantly lower incidence of PROM. Conversely, primiparity was significantly associated with a higher rate of PROM (52.75%; p = 0.0115). Vaginal delivery was more frequent in cases with PROM (64.68%). Neonatal hospitalization showed a decreasing trend (R² = 0.7156). Transfer to a tertiary NICU was significantly correlated with lower gestational age and lower Apgar scores. Conclusion The incidence of preterm birth in the observed region is stable and relatively low. The study highlights two distinct patterns of preterm delivery: spontaneous preterm labor associated with PROM and vaginal delivery in primiparous women, versus medically indicated preterm delivery driven by maternal comorbidities like hypertension and obesity, resulting in higher cesarean section rates. Effective antenatal management of these comorbidities is crucial for improving perinatal outcomes.