Unraveling the mysteries of spiral artery remodeling.

Spiral artery remodeling is the process by which the uterine vessels become large bore low resistance conduits, allowing delivery of high volumes of maternal blood to the placenta to nourish the developing fetus. Failure of this process is associated with the pathophysiology of most of the major obstetric complications, including late miscarriage, fetal growth restriction and pre-eclampsia. However, the point at which remodeling 'fails' in these pathological pregnancies is not yet clear. Spiral artery remodeling has predominantly been described in terms of its morphological features, however we are starting to understand more about the cellular and molecular triggers of the different aspects of this process. This review will discuss the current state of knowledge of spiral artery remodeling, in particular the processes involved in loss of the vascular smooth muscle cells, and consider where in the process defects would lead to a pathological pregnancy.