The renin-aldosterone system during normal and hypertensive pregnancy

Gestational hypertension complicates approximately 5%-7% of pregnancies and it may be deleterious to both maternal and fetal health. Gestational hypertension is a multisystem disorder which always resolves itself after delivery; its primary pathology still remains incompletely clarified. The renin-aldosterone system is a major determinant of sodium balance in pregnancy. To evaluate the changes in renin and aldosterone levels during normal and hypertensive pregnancy we undertook this study. Plasma renin activity and aldosterone levels were measured in 71 pregnant (43 normotensive, 28 hypertensive) and 24 non-pregnant (12 normotensive, 12 hypertensive) women, aged 19-43 years (mean +/- SD 28 +/- 2.8). Women were allocated into the following five groups: Groups 1 and 2 consisted of 12 normotensive and 12 hypertensive non-pregnant women, respectively; group 3 consisted of 20 women (14 normotensive and 6 hypertensive) at 11-19 weeks of gestation; group 4 consisted of 24 women (14 normotensive and 10 hypertensive) at 20-29 weeks of gestation, and group 5 consisted of 27 women (15 normotensive and 12 hypertensive) at 30-37 weeks of gestation. Both plasma renin activity and aldosterone levels progressively increased during normotensive pregnancy and were higher compared to normotensive non-pregnant women. Among hypertensive pregnant women, plasma renin activity levels remained unchanged during the three trimesters of pregnancy and were higher compared to hypertensive non-pregnant women. Only during the third trimester did aldosterone levels significantly increase in hypertensive pregnant women, compared to hypertensive non-pregnant women. Despite stable renin levels, aldosterone levels increased significantly during the third trimester of hypertensive pregnancy. Thus, we conclude that aldosterone biology seems to be directly or indirectly involved in the etiology of gestational hypertension independently of renin levels.