Several aspects of coarctation of the aorta conform with the concept of a deformation, a disorder of morphogenesis resulting from altered fetal hemodynamics. Based on its location at the junction of the aortic isthmus and the ductus arteriosus, the continuity of the ductal wall with the fibromuscular curtain, and the association with cardiovascular malformations causing decreased blood flow through the ascending aorta, coarctation of the aorta is interpreted as the result of diminished blood flow through the fetal aorta, which leads to persistence and aggravation of the normally narrow isthmus and subsequent development of the curtain.