Background: In the diagnosis and treatment of macrosomia, which is related to birth pain, asphyxia, and maternal morbidity, estimating foetal weight may be critical.Fetal abdominal subcutaneous tissue thickness (FASTT) is one such ultrasound parameter that is an independent consideration in predicting big babies and can estimate foetal weight for high for gestational age babies when substantiated with other ultrasound parameters.The aim of this study was to determine the importance of using ultrasonography to measure subcutaneous tissue thickness in predicting foetal birth weight. Patients and methods: This prospective observationl study included 276 pregnant women at term admitted to the obstetric ward and scheduled for elective Cesarean section or induction of labor or during labor. Ultrasonographic evaluation was done immediate before delivery for measurement of the thickness of the subcutaneous fat tissue at the anterior abdominal wall was done three times and the average was taken. Ultrasonic estimation of fetalweight , actual birth weight immediately after delivery by a neonatologist in the delivery room using (SECA digital medical weighing) and the thickness of the subcutaneous fat tissue were recorded. Results:FASTTand birth weight were found to have a positive association. A responsive measure to predict large babies is the FASTT of 6.85 mm. The FASTT test is not accurate enough to estimate the birth weight of small babies weighing less than 2500 grammes. Conclusion:Along with other established birth weight markers, FASTT may be used as a secondary predictor to forecast big for gestational age infants.