Sympathetic activation during early pregnancy in humans

• Published in: The Journal of physiology 2012-08, Vol.590 (15), p.3535-3543
• Main Authors: Jarvis, Sara S., Shibata, Shigeki, Bivens, Tiffany B., Okada, Yoshiyuki, Casey, Brian M., Levine, Benjamin D., Fu, Qi
• Format: Article
• Language: English
• Subjects: Adult; Aldosterone - blood; Blood pressure; Blood Pressure - physiology; Cardiovascular; Circulatory system; Female; Forearm - physiology; Heart Rate; Humans; Hypertension; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Peroneal Nerve - physiology; Preeclampsia; Pregnancy; Pregnancy - physiology; Pregnancy Trimester, First - physiology; Regional Blood Flow; Renin - blood; Sympathetic Nervous System - physiology
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2012.228262

Key points •  Sympathetic activity has been reported to increase in normotensive pregnant women, and to be even greater in women with gestational hypertension and preeclampsia at term. •  Whether sympathetic overactivity develops early during pregnancy, remaining high throughout gestation, or whether it only occurs at term providing the substrate for hypertensive disorders is unknown. •  We found that vasomotor sympathetic activity was markedly greater, diastolic pressure trended lower, total peripheral resistance decreased, sympathetic vascular transduction was blunted, and renin and aldosterone both were higher during early pregnancy (i.e. ≤8 weeks of gestation) than pre‐pregnancy. •  It is suggested that sympathetic activation is a common characteristic of early pregnancy in normotensive women. •  These results help us better understand blood pressure control mechanisms during normal pregnancy in humans.   Sympathetic activity has been reported to increase in normotensive pregnant women, and to be even greater in women with gestational hypertension and preeclampsia at term. Whether sympathetic overactivity develops early during pregnancy, remaining high throughout gestation, or whether it only occurs at term providing the substrate for hypertensive disorders is unknown. We tested the hypothesis that sympathetic activation occurs early during pregnancy in humans. Eleven healthy women (29 ± 3 (SD) years) without prior hypertensive pregnancies were tested during the mid‐luteal phase (PRE) and early pregnancy (EARLY; 6.2 ± 1.2 weeks of gestation). Muscle sympathetic nerve activity (MSNA) and haemodynamics were measured supine, at 30 deg and 60 deg upright tilt for 5 min each. Blood samples were drawn for catecholamines, direct renin, and aldosterone. MSNA was significantly greater during EARLY than PRE (supine: 25 ± 8 vs. 14 ± 8 bursts min−1, 60 deg tilt: 49 ± 14 vs. 40 ± 10 bursts min−1; main effect, P < 0.05). Resting diastolic pressure trended lower (P= 0.09), heart rate was similar, total peripheral resistance decreased (2172 ± 364 vs. 2543 ± 352 dyne s cm−5; P < 0.05), sympathetic vascular transduction was blunted (0.10 ± 0.05 vs. 0.36 ± 0.47 units a.u.−1 min−1; P < 0.01), and both renin (supine: 27.9 ± 6.2 vs. 14.2 ± 8.7 pg ml−1, P < 0.01) and aldosterone (supine: 16.7 ± 14.1 vs. 7.7 ± 6.8 ng ml−1, P= 0.05) were higher during EARLY than PRE. These results suggest that sympathetic activation is a common characteristic of early pregnancy in humans despi