Plasma renin concentration throughout healthy and hypertensive pregnancy: a systematic review and meta-analysis

Objective. Pregnancy is characterized by profound circula­tory changes and compensatory adjustments in the renin-an­giotensin-aldosterone system (RAAS). Differences in the regulatory response of the RAAS may antedate or accom­pany vascular complicated pregnancy. Therefore, we aim to delineate the trajectory of active plasma renin concentration (APRC) in healthy and complicated pregnancies.
Materials and Methods. We performed a systematic review and meta-analysis on APRC during normotensive and hyper­tensive pregnancies, for which we searched PubMed (NCBI) and Embase (Ovid) databases. We included only studies re­porting measurements during pregnancy together with a nonpregnant reference group measurement. Risk of bias was assessed with QUIPS. Ratio of the mean (ROM) and 95% con­fidence intervals (CI) of APRC values between pregnant and nonpregnant women were estimated for predefined intervals of gestational age using a random-effects model. A meta-re­gression analysis was used to analyse APRC over time.
Results. In total, we included eighteen studies which pro­vided APRC values of 465 healthy pregnancies, 244 compli­cated pregnancies and 410 nonpregnancies. As compared to nonpregnancy, APRC significantly increased as early as the first weeks of healthy pregnancy and stayed consistently in­creased throughout the whole pregnancy (ROM 2.77; 95%CI 2.26-3.39). In contrast, APRC in hypertensive complicated pregnancy was not significantly different from nonpregnancy (ROM 1.30; 95%CI 0.96-1.76).
Conclusions. Our findings show that healthy vascular adap­tation in pregnancy is accompanied with an increase in APRC levels. In hypertensive pregnancies this increase in APRC is not observed, which might suggest that renin released is sup­pressed by the high blood pressure in these pregnancies.