OBJECTIVE: Prior studies have suggested that macrosomia is a morbid condition associated with gestational diabetes mellitus. We sought to determine whether ecographic and Doppler studies are useful tools for the prediction of macrosomia and other perinatal morbid conditions in pregnancies complicated by diabetes mellitus. STUDY DESIGN: Sixty cases were included in this study, 20 were diabetics, 20 were diabetics with fetal macrosomia (diagnosed clinically and by ultrasound) and 20 were control non-diabetic group (between 36-37 weeks’ gestation). All patients were subjected to composite ultrasound gestational age determination, Estimating fetal weight, placental grade assessment, fetal biophysical profile, Uterine artery Doppler, Umbilical artery Doppler, Middle cerebral artery Doppler. Fetal outcome was assessed using through clinical examination to detect Apgar score, birth weight, serum glucose level (neonatal hypoglycemia is detected by a fetal blood glucose level less than 35 mg% for term infants and 25 mg% for preterm infants at ½ to 1 hour after delivery according to Tyrala, 1996), congenital anomalies and the development of respiratory distress syndrome.RESULTS: In the Macrosomia group versus the diabetic group there were significant difference between uterine artery Doppler (p<0.05), umbilical artery Doppler (p<0.05), middle cerebral artery Doppler (p<0.05).The mean time of delivery for the 3 groups was 39.6 +/- 0.6, 38.4 +/- 0.8 and 38.3 +/- 0.5 for group 1, group 2 and group 3 respectively. By studying the 1-minute Apgar score and the 5-minute Apgar score, there was significant difference between group 1 and group 2 (p<0.05), group 1 and group 3 (p<0.05) and no significance between group 2 and group 3. Rates of neonatal hypoglycemia among group 3 and group 2 (30% vs 15%, p<0.0001) showed a significant difference.CONCLUSIONS: This study suggests that unrecognized gestational diabetes increases risks of large for gestational age infants, macrosomia, In maternal diabetes mellitus, increased impedance to flow in the umbilical artery is associated with the development of pre-eclampsia and/or intrauterine growth restriction. There is contradictory evidence concerning a possible increase in impedance in pregnancies with maternal vasculopathy.