Doppler interrogation of the uterine arteries provides information on the physiologic transformation of the spiral arteries during pregnancy. Lack or suboptimal conversion of such arteries by the late second or third trimester of pregnancy is a strong indicator of increased risk for adverse pregnancy outcome, in particular, iatrogenic prematurity due to severe fetal growth restriction or preeclampsia. Uterine artery Doppler can thus play a role in the presence of medical conditions antedating pregnancy, which have greater risk of abnormal placentation, like chronic hypertension, to identify the subgroup with increased pregnancy complications and adverse outcome. In the presence of pregnancy complications related to inadequate placentation, such as fetal growth restriction or preeclampsia, uterine artery Doppler also plays a role, as abnormal findings signal increased severity of the disease and thus greater likelihood of unfavorable perinatal outcome.