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Changes in 24-hour heart rate variability during normal pregnancy.
P K Stein1, M T Hagley, P L Cole
1Division of Cardiology, Washington University School of Medicine and Barnes-Jewish Hospital, St Louis, Missouri, USA.
American Journal of Obstetrics and Gynecology
|April 16, 1999
Summary
Maternal heart rate variability significantly decreases early in pregnancy, with most changes occurring within the first six weeks. Individual responses during pregnancy show notable variation.
Area of Science:
- Cardiovascular Physiology
- Maternal Health
- Autonomic Nervous System Function
Background:
- Pregnancy significantly impacts maternal physiology.
- Understanding cardiovascular autonomic modulation during pregnancy is crucial for maternal health.
- Heart rate variability (HRV) serves as a noninvasive marker for autonomic function.
Purpose of the Study:
- To investigate the effects of normal pregnancy on heart rate variability.
- To assess maternal cardiovascular autonomic modulation throughout gestation.
- To determine the timing of these physiological changes.
Main Methods:
- Utilized 24-hour Holter recordings in healthy pregnant volunteers.
- Collected data at multiple gestational points: early pregnancy (<=6 weeks), 10, 18, and 34 weeks, and non-pregnant state.
- Analyzed heart rate variability indices and nighttime respiratory rates.
Main Results:
- Maternal heart rate variability demonstrated a significant decline during pregnancy.
- Most HRV indices were decreased in early pregnancy compared to the non-pregnant state.
- Respiratory rate increased, and changes between subsequent stages were modest, with significant individual variability observed.
Conclusions:
- The primary alterations in cardiac autonomic modulation and respiration occur within the initial six weeks of conception.
- Significant individual variability exists in heart rate and heart rate variability changes throughout normal pregnancy.