Background: The ultrasound estimation of fetal weight through Bi Parietal Diameter, Abdominal Circumference, Head Circumference and Femur Length is an important component in obstetrics since it is directly related to gestational age, which assists in the planning of the mode of delivery and labour management. It offers information on IUGR (intrauterine growth restriction) and is useful in preventing preterm delivery. It also helps to reduce prenatal morbidity and mortality. Aim and objectives: To assess The Accuracy of Incorporation of Fetal Thigh Circumference in The Formula of Estimating Birth weight. Methods: This cross-sectional study was performed at Minia University, Maternity and Children Hospital from January 2021 to December 2022. The study included 1000 singleton pregnant women admitted for planned delivery at term (between 36-40 weeks) either by elective cesarean section with different obstetric indications or by induction of labour and vaginal delivery. Results: The maternal ages ranged from 24 to 40, with a mean of 31.95 ± 3.08 years. The value of mid-thigh circumference (measured in centimeters) varied from 3.6 to 29.9, with an average of 12.96 ± 6.86. The estimated birth weight (BW) and actual BW were determined by Hadlock and Vintzileos. The mean actual BW in was 3.1 ± 0.59. The estimated BW according to Hadlock's method varied from 2.03 to 4.08, with a mean value of 3.05 ± 0.62. While, Vintzileos' estimated birth weight ranged from 2.29 to 4.66, with a mean of 3.16± 0.64. Conclusion: The measurement of fetal thigh circumference with other parameters enhances the accuracy, sensitivity, and specificity in estimating intra-uterine fetal weight. The application of Vintzileos' formula might be beneficial in routine clinical practice for estimating fetal weight.