This study investigates the pressor response to angiotensin II (A-II) in primigravida patients throughout pregnancy to understand when resistance to A-II develops, the physiological sequence leading to this resistance, and whether sensitivity to A-II can be detected before the onset of pregnancy-induced hypertension (PIH). The study involved 192 patients, with 120 remaining normotensive and 72 developing PIH. Both groups showed vascular resistance to A-II as early as the 10th week of pregnancy, but the maximum resistance occurred at different stages. Normotensive patients reached their peak resistance at 18-30 weeks, while those with PIH reached it at 18 weeks. By 22 weeks, a clear separation was observed, with the normotensive group requiring higher doses of A-II. The study also found that sensitivity to A-II decreased in normotensive patients by 26 weeks, 12-14 weeks before the onset of PIH. Additionally, the development of sensitivity to A-II in PIH patients was not preceded by significant changes in blood pressure or proteinuria. The findings suggest that a screening test at the beginning of the third trimester could predict PIH with high accuracy.This study investigates the pressor response to angiotensin II (A-II) in primigravida patients throughout pregnancy to understand when resistance to A-II develops, the physiological sequence leading to this resistance, and whether sensitivity to A-II can be detected before the onset of pregnancy-induced hypertension (PIH). The study involved 192 patients, with 120 remaining normotensive and 72 developing PIH. Both groups showed vascular resistance to A-II as early as the 10th week of pregnancy, but the maximum resistance occurred at different stages. Normotensive patients reached their peak resistance at 18-30 weeks, while those with PIH reached it at 18 weeks. By 22 weeks, a clear separation was observed, with the normotensive group requiring higher doses of A-II. The study also found that sensitivity to A-II decreased in normotensive patients by 26 weeks, 12-14 weeks before the onset of PIH. Additionally, the development of sensitivity to A-II in PIH patients was not preceded by significant changes in blood pressure or proteinuria. The findings suggest that a screening test at the beginning of the third trimester could predict PIH with high accuracy.