Muscle sympathetic nerve activity peaks in the first trimester in healthy pregnancy: a longitudinal case study

• Published in: Clinical autonomic research 2017-12, Vol.27 (6), p.401-406
• Main Authors: Hissen, Sarah L., El Sayed, Khadigeh, Macefield, Vaughan G., Brown, Rachael, Taylor, Chloe E.
• Format: Article
• Language: English
• Subjects: Adrenergic Fibers - physiology; Adult; Baroreceptors; Baroreflex - physiology; Blood pressure; Blood Pressure - physiology; Cardiology; Diabetes; Endocrinology; Female; Gastroenterology; Heart diseases; Heart rate; Heart Rate - physiology; Humans; Infant, Newborn; Longitudinal Studies; Medicine; Medicine & Public Health; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Neurology; Ophthalmology; Pregnancy; Pregnancy Trimester, First - physiology; Reflexes; Short Communication; Sympathetic Nervous System - physiology
• ISSN: 0959-9851; 1619-1560
• DOI: 10.1007/s10286-017-0439-1

Objective and methods Muscle sympathetic nerve activity and baroreflex sensitivity were examined at rest before, during (weeks 6, 11, 17, 22, 25, 33 and 36) and after a normotensive pregnancy. Results Muscle sympathetic nerve activity is elevated during pregnancy with a large peak in the first trimester (Δ17 bursts/min) and a secondary peak in the third trimester (Δ11 bursts/min). Cardiac baroreflex sensitivity peaked in the first trimester (10 vs. 6 ms/mmHg pre-pregnancy), whereas sympathetic baroreflex sensitivity was greater throughout. Interpretation The increase in sympathetic outflow early in pregnancy cannot be explained by a reduction in baroreflex sensitivity, while the secondary increase in burst frequency in the third trimester may, in part, be explained by the elevated heart rate.