Background: Intrauterine growth retardation (IUGR) is an obstetrical syndrome that is generally associated with increased mortality and morbidity. In IUGR, maternal placental blood flow is extremely compromised and that worsen the inter-villous circulation leading to an end-stage fetal distress. Objective: To compare TCD/AC ratio in both normal and growth restricted fetuses in second and third trimesters and to find if there is any correlation between TCD/AC ratio and EFW. Patients and methods: The study was conducted on 100 singleton pregnant women at EL-Sayed Galal University Hospital and Damanhour Teaching Hospital in the period between March 2019 till May 2020 and the patients were divided into two main equal groups. Group I included pregnant females with normally growing fetuses and Group II included pregnant females with growth restricted fetuses above 20 weeks of gestation. Results: This study demonstrated the usefulness of the single cut-off value (13.75%) of the TCD/AC ratio which may contribute to the early identification of SGA infants. The problem lied in identifying the process at the onset or before the IUGR has become severe. Usually the first parameter to decrease is the fetal AC due to depletion of hepatic glycogen and subcutaneous fat stores. The TCD/AC ratio, which utilized a single cut-off value (13.75%) independent of GA, improved diagnostic sensitivity and specificity in these cases. The possible contribution of the TCD/AC ratio in identifying the fetal growth failure itself, which was more important than predicting weight at birth to be further evaluated. There was no correlation between TCD/AC ratio and EFW and no statistical significant correlation between TCD/AC ratio and UA Doppler. Conclusion: In IUGR fetuses, the fetal TCD was less affected than fetal head circumference (HC) suggesting preferential preservation of cerebellar growth relative to other cranial structures. The TCD/AC ratio was helpful in recognizing abnormal fetal growth even when the GA was uncertain since this ratio was gestational age-independent.