Effects of human pregnancy on cardiac autonomic function above and below the ventilatory threshold

• Published in: Journal of applied physiology (1985) Vol. 90; no. 1; pp. 321 - 328
• Main Authors: Avery, N. D, Wolfe, L. A, Amara, C. E, Davies, G. A. L, McGrath, M. J
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01-01-2001; American Physiological Society
• Subjects: Adult; Autonomic Nervous System - physiology; Biological and medical sciences; Differential Threshold; Effects; Epinephrine - blood; Exercise; Female; Functions; Fundamental and applied biological sciences. Psychology; Heart; Heart Conduction System - physiology; Humans; Lactic Acid - blood; Mother. Fetoplacental unit. Mammary gland. Milk; Norepinephrine - blood; Oxygen Consumption; Pregnancy; Pregnancy - physiology; Pregnancy. Parturition. Lactation; Reference Values; Respiratory Physiological Phenomena; Respiratory system; Spectrum analysis; Vertebrates: reproduction; Physical exercise; Human; Cardiovascular control; Variability; Gestational age; Pregnancy; Heart rate; Ventilatory response; Autonomic nervous system; Baroreflex; Female; Pulmonary ventilation; Respiration; Parasympathetic nervous system; Threshold
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.90.1.321

3  Department of Obstetrics and Gynaecology
and 2  Department of Physiology,
1  School of Physical and Health Education,
Queen's University, Kingston, Ontario, Canada K7L 3N6
This study examined the effects
of human pregnancy on heart rate variability (HRV), spontaneous
baroreflex (SBR) sensitivity, and plasma catecholamines at rest and
during exercise. Subjects were 14 healthy, physically active pregnant
women (PG; mean gestational age = 33.9 ± 1.0 wk). Results
were compared with an age-matched nonpregnant control group (NPG;
n  = 14) with similar characteristics. The
electrocardiographic R-wave-R-wave interval and systolic blood pressure (via finger plethysmograph) were measured on a beat-to-beat basis at rest and during upright cycling at 60 and 110% of the ventilatory threshold (T vent ). Parasympathetic nervous
system (PNS) modulation (as reflected by HRV high-frequency/total power and SBR slope) was significantly reduced at rest in the PG vs. the NPG.
During exercise, PNS modulation decreased significantly in both groups,
but the magnitude of PNS withdrawal from rest to 110%
T vent was smaller in the PG vs. NPG. Sympathetic nervous system (SNS) modulation (reflected by the low-frequency
power-to-high-frequency power ratio) increased above resting values at
60 and 110% T vent in the NPG. SNS modulation at 110%
T vent was significantly lower in the PG compared with the
NPG. Plasma norepinephrine and epinephrine levels were also lower at
110% T vent in the PG. It was concluded that healthy
pregnant women exhibit lower PNS modulation at rest and blunted SNS
modulation during exercise above T vent in late gestation.
spectral analysis; spontaneous baroreflex function; human
gestation; exercise intensity