Maternal obesity is an epidemic in the developed world like Egypt. There are many pregnancy-associated complications including pre-eclampsia, gestational diabetes, and increased rates of septic wound after cesarean delivery. As a potential explanation of the etiology of complications due to maternal obesity, the role of endothelial dysfunction in the systemic and peripheral vasculatures has been hypothesized. It has been proposed that some adverse pregnancy outcomes in obese patients may be mediated by placental insufficiency. Utero-placental insufficiency is typically associated with fetal growth restriction and low birth weight. Umbilical and uterine artery Doppler is widely accepted as a useful tool for monitoring high-risk pregnancies. Normally, uterine artery vascular impedance gradually decreases until the late mid-trimester, owing to the establishment of a low-resistance placental circulation. Obesity has little impact on uterine vascular changes reflected by the early uterine artery PI. However, in the second trimester, extreme obesity appears to impair the normal continued drop in uterine vascular resistance. Many studies have examined the relationship between BMI and Doppler changes in high-risk pregnancies, but few have addressed these changes in low-risk pregnancies.