Ultrasound investigation is peculiar when pregnancy is complicated by gestational diabetes. One have to study interventricular septal thickness and to predict macrosomia. Before delivery septal thickness should be under 6 mm. Estimated fetal weight (EFW) and abdominal circumference (AC) are accurate to detect macrosomia. Quite all formulas of EFW are not significantly different. An EFW of 4,000 gm have a sensitivity of 45% and positive predictive value of 81% to predict macrosomia. AC >=35 cm have a negative predictive value of 99% and AC >=37 cm have a positive predictive value of 91% to predict an EFW of 4,000 gm. Soft-tissue measurements are used to evaluate the increase of fetal fat body mass. Cheek to cheek diameter, upper arm subcutaneous tissue, shoulder subcutaneous tissue can be used. Three-dimensional ultrasonography may offer volume assess of the thigh or upper arm.