Beyond the placental bed: placental and systemic determinants of the uterine artery Doppler waveform.

The uterine artery Doppler waveform has been extensively investigated, though its widespread clinical use as a predictor of adverse pregnancy outcome remains under debate. The determinants of the waveform have classically been ascribed to transformation of the spiral arteries and the development of a low resistance uteroplacental circulation, failure of which predisposes to pre-eclampsia, fetal growth restriction and other adverse outcomes. It has become increasingly evident that although spiral artery transformation determines in some part the characteristics of the Doppler waveform, factors pertaining to maternal vascular and endothelial function are also important.