: Diabetes mellitus is one of the commonest  problem encountered in pregnancy. In Asia, the incidence is around 5–8%.Fetal macrosomia complicates more than 10% of all pregnancies. Macrosomia is associated with significant fetal, neonatal and maternal risks. AIM: To evaluate the sonographic measurement of umbilical cord thickness, fetal fat layer and shoulder pad thickness as predictors of macrosomia in fetus of women with gestational and pregestational diabetes mellitus. MATERIALS AND METHODS: This study was conducted for a period of one year fromApril 2015 to March 2016, at the  Institute of Obstetrics and Gynecology, Egmore. Antenatal women with GDM or PRE GDM, diagnosed by OGTT , dates confirmed by early scans in their late third trimester (35–36 weeks) who attended Antenatal OPD at IOG, were recruited prospectively into the study. CONCLUSIONS:  Among the ultrasound parameters, a cut of abdominal circumference  >35 cms ,fetal fat layer>5mm,had good sensitivity , specificity and negative predictive value as predictors of macrosomia. Umbilical cord thickness greater than 90^th percentile had  good negative predictive value.