Abstract: Objective To investigate the clinical factors influencing the closure time of the ductus arteriosus in preterm infants and analyze its association with common complications in this population.Methods Preterm infants, gestational age <32 weeks or birth weight <1500 g, who were admitted to the Neonatal Intensive Care Unit of the Affiliated Hospital of Xuzhou Medical University between August 2021 and August 2024 and diagnosed with patent ductus arteriosns (PDA) by echocardiography within 72 h of admission were selected. Based on the time of ductal closure, the patients were divided into three groups: closure within 2 weeks after birth, between 2-4 weeks, and after 4 weeks. Their general information, maternal pregnancy history, initial echocardiographic parameters, initial platelet parameters after PDA diagnosis, treatment details during hospitalization, and complication occurrences were collected and compared among groups. Univariate analysis and multivariate logistic regression were used to identify factors associated with closure time and to evaluate the relationship between closure time and complications.Results A total of 268 preterm infants were included. Multivariate analysis identified ductal diameter (P=0.002,95%CI:2.860-130.595), right atrial diameter (P=0.030,95%CI:0.118-0.894), duration of invasive mechanical ventilation (P=0.033,95%CI:1.010-1.258), platelet count (P<0.01,95%CI:0.838-0.951), and proportion of large platelets (P<0.001,95%CI:0.279-0.658) as independent risk factors for delayed closure (P<0.05). Compared with the group whose PDA closed within 2 weeks, the group with closure after 4 weeks had significantly increased risks of moderate-to-severe bronchopulmonary dysplasia (BPD) (P<0.001, 95%CI:3.817-16.775) and necrotizing enterocolitis (NEC) (P<0.001,95%CI:1.227-8.782).Conclusions Larger ductal diameter, smaller right atrial diameter, prolonged invasive mechanical ventilation, decreased platelet count, and reduced proportion of large platelets are independent risk factors for delayed closure in preterm infants. Persistent PDA beyond 4 weeks after birth significantly increases the risk of moderate-to-severe BPD and NEC, which warrants early identification and intervention.