Figure 105

Functional significance of the stimulated renin-angiotensin system (RAS) in pregnancy. We determine whether changes in the RAS in pregnancy are primary, and the cause of the increase in plasma volume, or whether these changes are secondary to the vasodilation and changes in blood pressure. To do so, we administered a single dose of captopril to normotensive pregnant women in their first and second trimesters and age-matched normotensive women who were not pregnant. We then measured mean arterial pressure (MAP) and plasma renin activity (PRA) before and 60 minutes after the dose.

A, Despite similar baseline blood pressures, blood pressure decreased more in pregnant women compared with those who were not pregnant in response to captopril. This observation suggests that the RAS plays a greater role in supporting blood pressure in pregnancy. B, Baseline PRA was higher in pregnant women compared with those who were not pregnant, and pregnant women had a greater increase in renin after captopril compared with those who were not pregnant. T—time. (From August and coworkers [8]; with permission.)

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