Objective:Patent ductus arteriosus is an important problem in preterms. We aimed to investigate the relation of patent ductus arteriosus with shunt index. Methods:The preterm infants with a birth weight of <= 1500 g and/or gestational age of <30 weeks and an indication for umbilical artery and venous catheterization formed the study group. Between the postnatal 24-48 hours, the first arterial and venous blood samples were obtained and the patients were evaluated by echocardiography. In patients with hemodynamically significant patent ductus arteriosus (patient group), during the first 24 hours after the competition of the first course of medical treatment, the second blood samples were obtained and echocardiography repeated. In patients without patent ductus arteriosus (control group), second blood samples were taken after the postnatal 72 hours. Also, echocardiography was performed. Results:A total of 60 infants, (female = 29, male = 31), were included in the study. We did not find a statistically significant relation between shunt index and the presence of patent ductus arteriosus (p > .05). A statistically significant positive correlation between the fraction of inspired oxygen and shunt index was found. As the postnatal ages progressed, the shunt index values tended to decrease significantly. Conclusion:Our results suggest that shunt index cannot be used as an indicator of hemodynamically significant patent ductus arteriosus in preterm infants. The postnatal age and fraction of inspired oxygen have a significant effect on shunt index in these patients. It was thought that the other possible factors that affect the shunt index should be investigated in preterms between certain postnatal ages.