Physiological implications of arteriovenous anastomoses and venous hemodynamic dysfunction in early gestational uterine circulation: a review

This review summarizes current information on anatomical and physiological properties of the early gestational uteroplacental circulation, and implications of normal or abnormal functioning of the venous compartment. It is illustrated that these properties serve intra-uterine redistribution of blood flow, which is a crucial activity during different stages of trophoblastic remodelling of spiral arteries. Maintaining conditions of pressure and flow constant in the developing intervillous space is important towards normal functioning of the placenta in advanced pregnancy. Failure of this process predisposes to damage of trophoblastic villi, which is commonly seen in preeclampsia and/or fetal growth restriction. Basic principles of vascular physiology allow linking venous hemodynamic dysfunction to increased intervillous pressure. From this, it is concluded that current methods to explore the uteroplacental circulation in normal pregnancy and preeclampsia should be expanded with integrative methods focussing on each site of the microvascular network, the arterial ànd the venous compartment.