Autonomic changes during pregnancy: assessment by spectral heart rate variability analysis

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Function
• Reproductive Medicine

Background:

• Cardiovascular autonomic balance is crucial for maintaining homeostasis.
• Pregnancy involves significant physiological adaptations, including changes in autonomic tone.
• Understanding these changes is vital for maternal and fetal well-being.

Purpose of the Study:

• To investigate alterations in cardiovascular autonomic balance during normal pregnancy.
• To analyze heart rate variability (HRV) using spectral analysis to assess sympathovagal balance.
• To compare autonomic function in pregnant versus nonpregnant women across gestation.

Main Methods:

• Electrocardiograms (ECGs) were recorded in 32 pregnant women (10-39 weeks gestation) and 8 nonpregnant controls.
• Spectral analysis of HRV was performed to calculate the low-frequency/high-frequency (LF/HF) peak ratio, an index of sympathovagal balance.
• Measurements were taken in left lateral recumbency, supine position, and during low-intensity handgrip exercise.

Main Results:

• Pregnant women exhibited a lower LF/HF ratio compared to controls, indicating a shift towards vagal predominance.
• The LF/HF ratio significantly increased in pregnant women when changing from left lateral to supine position after 33 weeks gestation.
• Low-intensity handgrip exercise increased the LF/HF ratio in both pregnant and nonpregnant women, but the response differed between groups.

Conclusions:

• Normal pregnancy is associated with a significant rearrangement of autonomic tone.
• This autonomic shift may represent a relative vagal predominance or be secondary to baroreflex attenuation.
• HRV spectral analysis provides valuable insights into cardiovascular autonomic regulation during pregnancy.