OBJECTIVE: To evaluate the association of aortic isthmus (AoI) circulation assessed by doppler imaging in growth restricted fetuses with perinatal outcome. DESIGN: prospective longitudinal observational study. SETTING- Tertiary referral center POPULATION- Intrauterine growth restriction (IUGR) (n=38) between 24–36 weeks’ gestation. METHODS- Doppler examination in aortic isthmus, umbilical artery (UA), middle cerebral artery(MCA), and ductus venosus(DV) was performed. The relation between antegrade (n = 25) and retrograde flow (n = 13)in AoI ,other Doppler parameters with perinatal outcome was analyzed. RESULTS: Retrograde AOI group had higher rates of adverse perinatal outcome (92.3% vs. 72%) with 63.1% sensitivity and 87.5% specificity. Overall perinatal mortality (intrauterine death and neonatal death) was higher in retrograde group (23%).No perinatal mortality in antegrade AoI group. Cases with absent end diastolic flow (AEDF) or reverse end diastolic flow (REDF) in the UA and retrograde flow in AoI and normal DV flow had 40% prenatal mortality as 25% in those with abnormal DV Doppler . CONCLUSION: Rretrograde blood flow in AoI is associated with adverse perinatal outcome, particularly intrauterine demise, neonatal death, RDS and increased duration of NICU stay. Even though the DV flow is normal adverse outcome might be suspected in fetuses with AEDF/REDF in UA and retrograde flow in AoI. Thus, retrograde flow in AoI might be considered as an additional trigger for delivering IUGR fetuses 30-34 weeks with AREDF in UA but requires further evaluation by large longitudinal studies . Keywords - Intrauterine growth restriction, doppler ultrasonography; fetal aortic isthmus; perinatal outcome .