Objective: To evaluate the accuracy of three different ultrasound formulas in estimation of fetal weight in suspected macrosomia early in labour. Design: A prospective clinical trial. Setting: Department of Obstetrics & Gynecology, Cairo University. Participants: Pregnant females presenting in early labour with clinical impression of macrosomia were examined by ultrasound and those with abdominal circumference more or equal to 35cm were selected for the study. Interventions: Every woman was considered as herself control and fetal weight was calculated using Campbell & Wilkin, Hadlock et al. and Shepard et al., formulas. The expected fetal weight was then compared by the real fetal weight. Results: There is no difference between different formulas for estimation of fetal weight in suspected macrosomic babies as proved by different statistical methods. There was a good correlation between the expected fetal weight estimated by different formulas with the real fetal weight. Conclusion: Prediction of macrosomia early in labour provides reliable data that can help in decision making with reasonable accuracy of different formulas.