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

autonomic function above and below the ventilatory thresh-old. J Appl Physiol 90: 321–328, 2001.—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 gesta-tional age 5 33.9 6 1.0 wk). Results were compared with an age-matched nonpregnant control group (NPG; n 5 14) with similar characteristics. The electrocardiographic R-wave-R-wave interval and systolic blood pressure (via finger plethys-mograph) were measured on a beat-to-beat basis at rest and during upright cycling at 60 and 110 % of the ventilatory threshold (Tvent). 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