Figure 2: The amount of angiotensin required to raise blood pressure by 20 mm Hg. This figure demonstrates two important findings obtained from serial observations in primiparas. Women undergoing physiologic pregnancy (■) become resistant to the pressor effect of infused angiotensin II by 14 weeks of gestation. They require significantly higher dose of angiotensin II to increase blood pressure by 20 mm of Hg. In contrast, women destined to develop preeclampsia (♦) regain their sensitivity to angiotensin II between 22–26 weeks of gestation, well before any other clinical manifestations of preeclampsia are appreciated [7].