The renin-angiotensin system is involved in the physiology of pregnancy in two ways. Circulating angiotensin II affects blood pressure, renal hemodynamics, and uteroplacental blood flow. Abnormalities in angiotensin II production rates in hypertensive pregnancy contribute to the hemodynamic changes seen in the disease. Additionally, there is a form of the renin-angiotensin system in kidney, ovary, and placenta whose function is regulated by prorenin. Prorenin, activated by a specific receptor, is involved in the regulation of steroid hormone biosynthesis and renal and uteroplacental blood flow.