Analysis of risk factors and prognostic differences in hospital-acquired thrombosis between very preterm infants and moderate to late preterm infants.

Objective: Neonates have the highest incidence of thrombosis among pediatric populations, and preterm infants are at a high risk of venous thrombosis, with its risk factors remaining inconclusive and treatment criteria remaining ununified. This study aimed to explore the high-risk factors for venous thrombosis in preterm infants with varying gestational ages and catheterisation types, and to clarify the clinical characteristics, treatment strategies, and short-term prognosis of neonatal venous thrombosis, to provide evidence for clinical decision-making. Methods: A retrospective cohort study was conducted on 282 preterm infants admitted to the Neonatal Intensive Care Unit of Peking University Third Hospital from January 2014 to December 2025, including 94 cases in the thrombosis group and 188 cases in the control group. Clinical data, including maternal prenatal information, infant basic information, diagnosis and treatment course, catheter-related information, and thrombosis-related details, were collected from the electronic medical record system. SPSS 27.0 software was used for statistical analysis using the Kruskal-Wallis test, Student's t-test and Mann-Whitney U test for continuous variables; chi-square test or Fisher's exact test for categorical variables; and univariate and multivariate logistic regression models and Firth's penalised likelihood logistic regression analyses were applied to identify independent risk factors for venous thrombosis in preterm infants. Results: The incidence of venous thrombosis was 0.45% in all hospitalised neonates and 1.0% in hospitalised preterm infants, with no significant differences in baseline data such as gestational age and birth weight between the two groups ( Conclusion: Lower extremity PICC placement is a core independent risk factor for venous thrombosis in preterm infants, with maternal anticoagulant use during pregnancy perhaps being a clinical predictor for all preterm infants. Neonatal venous thrombosis is mostly catheter-related, with a high proportion of asymptomatic cases, and routine vascular ultrasound can improve its detection rate. Individualised pharmacotherapy based on clinical manifestations and thrombus characteristics is associated with a favourable short-term prognosis, and timely adjustment of an abnormal catheter position is crucial for reducing thrombosis risk. Long-term follow-up is still needed for preterm infants with venous thrombosis to monitor for late adverse outcomes.