Background: Poor perinatal outcome and cerebral palsy have been linked to intrauterine growth restriction (IUGR). New Doppler metrics, like the aortic isthmus (AoI), can be used to detect and assess the severity of IUGR in fetuses. The aim of the current study is to investigate the better diagnosis of intrauterine growth Restriction using the aortic isthmus Doppler. Patients and methods: A cross-sectional study was conducted on 74 women with a singleton pregnancy between 24-34 weeks, with fetal growth restriction and placental insufficiency, between September 2021 and March 2022. Repeated Doppler evaluation of umbilical artery, middle cerebral artery and aortic isthmus artery were assessed until one day before pregnancy termination by 37 weeks. Correlation of Doppler findings with perinatal fetal outcomes was done. Results: As regard aortic isthmus artery resistance index (RI), it differed significantly between both groups as first visit, before termination, decrease and % decrease, as well as regard perinatal outcome as general anesthesia at delivery and neonatal ICU admission. Validity (area under the curve (AUC), sensitivity, specificity) for aortic isthmus, middle cerebral artery as well as umbilical artery at RI First visit to prognoses birth weight ≤2 kg where there was statistically significant difference between aortic isthmus, middle cerebral artery as well as umbilical artery (RI) first visit to prognoses birth weight ≤2 kg. Conclusion: Using Doppler imaging of the aortic isthmus to assess the clinical state of fetuses with fetal growth restriction (FGR) is possible, and even to decide when to terminate the pregnancy in preterm fetuses. Aortic isthmus (AI) Doppler measurements are useful to identify fetal growth restriction (FGR).