# Spiral Arteries --- **Spiral arteries** are special [[arteries]] in the [[uterus]] that change up in order to accommodate a developing [[placenta]] should one ever show up. Uteroplacental perfusion is *key* to fetal well-being, development, and growth, and spiral arteries facilitate that perfusion. When not pregnant, the uterine arteries and veins connect through the [[capillaries|capillary beds]] in the endometrium that you may expect. They are also connected via [[circulatory system|arteriovenous anastomoses]] in the myometrium, and the arteries have a distinctive spiral shape. When a pregnancy happens, the capillaries sort of disappear and spiral opens up into the [[placenta]] to dump blood around the [[placenta|chorionic villi]] where fetal gas exchange can happen. Uterine veins are also there for used up blood to go back. ![[spiral arteries.png]] ## Spiral Artery Remodeling When a [[pregnancy]] starts up, the trophoblast cells of what will become the [[placenta]] trigger the remodeling of the spiral arteries to ensure ample [[uteroplacental perfusion]]. By the end of the first trimester spiral remodeling is complete. Instead of connecting directly to capillaries and veins, the spiral arteries open up directly into the [[placenta]] and bathe the [[chorionic villi]] in oxygen and nutrient and antibody rich blood. ![[spiral artery remodeling.png]] Conditions such as [[preeclampsia]], though it doesn't show outside signs or symptoms so early in pregnancy, can negatively impact this process. In a normal pregnancy the spiral arteries open up as deep "V" shape, but in an abnormal pregnancy the opening is not only narrower, but the spirals are less spirally can lead to chronic hypertension. ___