Aim: The primary aim was to estimate premature infants' spontaneous patent ductus arteriosus closure rate. Secondly, to identify criteria associated with the chance of spontaneous closure. Methods:We performed a retrospective cohort study of 167 infants born before 32 weeks of gestation and diagnosed with a patent ductus arteriosus between 1 January 2008 and 31 December 2017. The spontaneous patent ductus arteriosus closure event rate was evaluated using the Kaplan-Meier estimator. Results:The spontaneous closure rate within the first year of life was 66% (95% CI 58%-73%), increasing to 80% (95% CI 72%-86%) five years after birth. When including both spontaneous closure and closure following treatment, 96% (95% CI 86%-100%) closed within 5 years after birth. The chance of spontaneous closure was reduced in the case of a large patent ductus arteriosus: OR 0.16 (95% CI 0.05-0.52), left atrial enlargement: OR 0.16 (95% CI 0.05-0.51), and pulmonary hypertension: OR 0.23 (95% CI 0.07-0.74). Conclusion:The chance of spontaneous closure in premature infants born between 23 and 32 weeks of gestation was high, and the incidence continued increasing until 5 years of follow-up.