Uteroplacental vascular adaptation and its failure in pre-eclampsia
THE CONTEXT
Normal pregnancy involves changes in spiral arteriolar blood flow and vascular responsiveness that help stabilize blood pressure.
Spiral arteriolar adaptation
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Physiological transformation makes the spiral arterioles a low-resistance, low-pressure, high-flow system.
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In pre-eclampsia, the second wave of endovascular trophoblast migration fails, reducing blood supply to the fetoplacental unit.
Blood pressure regulation in normal pregnancy
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Angiotensin-II is destroyed by angiotensinase released from the placenta.
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The vascular system becomes selectively refractory to the pressor action of angiotensin-II, mainly because of vascular synthesis of prostacyclin and nitric oxide.
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The vasodilator effects of prostacyclin and nitric oxide, together with angiotensin-II destruction, help stabilize blood pressure.