Objective:

To explore high-risk factors for venous thrombosis in preterm infants with varying gestational ages and catheterisation types, and to clarify clinical characteristics, treatment strategies, and short-term prognosis.

Approach:

• Study Design: A retrospective cohort study of 282 preterm infants admitted to the Neonatal Intensive Care Unit of Peking University Third Hospital from January 2014 to December 2025.

Key Findings:

• The incidence of venous thrombosis was 1.0% in hospitalised preterm infants.
• Right- and left-sided lower extremity PICC placement were identified as independent risk factors for venous thrombosis.
• Maternal use of anticoagulant or antiplatelet agents during pregnancy was a clinical predictor.
• 96% of thrombotic cases were associated with central venous catheterisation.
• The median time from catheterisation to thrombosis was 5 days, with 59% being deep vein thrombosis.

Interpretation:

Lower extremity PICC placement is a core risk factor for venous thrombosis in preterm infants, with a high proportion of asymptomatic cases detected through routine vascular ultrasound.

Limitations:

• The study is retrospective and may have inherent biases.
• The sample size may limit the generalizability of the findings.

Conclusion:

Individualised pharmacotherapy based on clinical manifestations and thrombus characteristics is associated with a favourable short-term prognosis.