Aim: To evaluate the relation between retrograde diastolic blood flow in the aortic isthmus and adverse perinatal outcome in fetuses with IUGR. Materials and Methods: The study included 33 fetuses with IUGR defined as the estimated fetal weight and abdominal circumference under the 10th percentile for a given gestational age. The Doppler examination of the blood flow in the aortic isthmus, umbilical artery, umbilical vein, middle cerebral artery, uterine arteries and ductus venosus was performed regularly. The study population was further divided into two subgroups, depending on the aortic isthmus blood flow direction, i.e. with and without retrograde isthmic diastolic flow. Furthermore, the relation between Doppler blood flow parameters and determinants of the perinatal outcome was analyzed. The perinatal outcome was reported as adverse if any of the following occurred: umbilical cord blood pH < 7,2; 5-minute Apgar score < 7; respiratory distress syndrome, intraventricular hemorrhage (III/IV grade); necrotizing enterocolitis; sepsis; intrauterine or neonatal death. Results: There was no statistically significant difference in the incidence of adverse perinatal outcome between the antegrade and retrograde isthmic blood flow groups. Moreover, the study showed no statistically significant relationship between the retrograde blood flow in the aortic isthmus and the prevalence of abnormal flow in the analyzed vessels. Conclusion: Retrograde diastolic blood flow in the aortic isthmus presents a low sensitivity and low predictive value in predicting the adverse perinatal outcome in pregnancies complicated with IUGR.