The interstitial EVT invades decidua and myometrium, where it anchors the conceptus and forms a continuous shell around it at the level of the decidua. Endovascular EVTs are associated with spiral arteries, either within the vessel wall (intramural) or replacing endothelium (intra-arterial). EVTs transform the narrow spiral arteries to wide uteroplacental arteries, which distribute blood into a low resistance vascular network.
