Changes in renin activity, aldosterone level and electrolytes in pregnancy-induced hypertension

In order to observe the sequential changes in the renin-angiotensin-aldosterone system (RAAS) in hypertensive pregnancies, blood and urine samples of pregnant women were collected every four weeks from the 20th week of gestation to the fourth week after delivery in a consecutive and prospective study. Nine subjects developed pregnancy-induced hypertension in later gestation, and six of them with proteinuria were classified as having preeclampsia. The gestational ages at the onset of hypertension were the 28th week for one patient, the 32nd week for three patients and the 36th week for five patients. Plasma renin activity in most of the cases decreased to non-pregnant levels after hypertension was established, while the plasma aldosterone level did not. Marked variations in daily sodium and potassium excretion were observed at the various gestational weeks, while serum concentrations of these electrolytes changed only within a narrow range. No correlation between the changes in RAAS and electrolytes were shown in our cases.