Maternal Uterine Vascular Remodeling During Pregnancy

Remodeling of the maternal uterine vasculature during pregnancy is a unique cardiovascular process that occurs in the adult and results in significant structural and functional changes in large and small arteries and veins, and in the creation of the placenta--a new fetomaternal vascular organ. This expansive, hypertrophic process results in increases in both lumen circumference and length, and is effected through a combination of tissue and cellular hypertrophy, endothelial and vascular smooth muscle hyperplasia, and matrix remodeling. This review summarizes what is currently known about the time course and extent of the remodeling process, and how local vs. systemic factors influence its genesis. The main focus is on upstream maternal vessels rather than spiral artery changes, although the latter are considered from the overall hemodynamic perspective. We also consider some of the underlying mechanisms and provide a hypothetical scenario that integrates our current knowledge. Abrogation of this adaptive vascular process is associated with several human gestational pathologies such as preeclampsia and intrauterine growth restriction (IUGR), which not only raise the risk of infant mortality and morbidity but are also a significant source of maternal mortality and susceptibility to cardiovascular and other diseases for both mother and neonate later in life.