Role of renin-angiotensin system in blood pressure regulation in pregnancy

We gave captopril (25 mg) to nine pregnant and eight non-pregnant women. From baseline to 60 min post-captopril, mean arterial pressure decreased significantly more in pregnant than in non-pregnant women (mean 15·0 [SE 2·5] vs 5·2 [1·2] mm Hg; difference 9·8 [95% Cl 3·9-15·9] mm Hg, P=0·0036), whereas plasma renin activity increased significantly more in the pregnant group (18·0 [5·5] vs 4·5 [1·9] ng mL-1 h-1; difference 13·5 [0·71-26·5], P=0·043). These findings support the hypothesis that stimulation of the renin-angiotensin system in pregnancy maintains blood pressure.