Studies of the renin-angiotension-aldosterone system, cortisol, DOC, and ADH in normal and hypertensive pregnancy.

Compared with a group of normal pregnant women, matched for age, parity, posture, and length of gestation, women with hypertension and proteinuria in the last trimester had significantly lower plasma concentrations of renin, renin substrate and angiotensin II. Plasma aldosterone and DOC concentrations were also lower in the hypertensive group. The plasma levels of cortisol, corticosterone, and ADH showed no significant difference. Plasma renin concentration was raised throughout normal pregnancy, and part of this increase appeared to be due to the presence of an inactive form of renin. Plasma concentrations of renin substrate, angiotensin II, and aldosterone were also raised in normal pregnant women, but concurrent measurement of these substances showed no significant relationship between them, renin, and plasma electrolytes in mid- or late gestation. A study of five women in the weeks immediately after conception showed increases in plasma angiotensin II and aldosterone concentrations, which were significantly related at this very early stage of pregnancy. Total 24-hour urinary sodium increased gradually from about two weeks after gestation to the end of the study five weeks later. This increase was due mainly to a rise in overnight sodium excretion, with a fall in the day/night ratio. No relationship was found between plasma angiotension II or aldosterone concentrations and day, night, or total 24 hour sodium excretion.