Key result
Advancing gestation in healthy pregnancies was associated with significant decreases in maternal vagal activity, heart rate complexity, and heart rate fragmentation.
Why the study?
Changes in maternal heart rate variability throughout pregnancy remain poorly understood, and standard assessments once per trimester may fail to capture complex and dynamic autonomic modulations.
Observational (n=29)
No
Effect estimate: Cohen's U1 0.214
Absolute Event Rate: 0.94% vs 1.4%
p-value: p=<0.0001
Longitudinal monitoring of maternal HRV during healthy pregnancy shows significant decreases in vagal activity, HR complexity, and HR fragmentation, reflecting dynamic autonomic adaptations to advancing gestation.
Hypothesis-generating for maternal autonomic monitoring; prospective validation needed before clinical use.
Changes in the maternal autonomic nervous system are essential in facilitating the physiological changes that pregnancy necessitates. Insufficient autonomic adaptation is linked to complications such as hypertensive diseases of pregnancy. Consequently, tracking autonomic modulation during progressing pregnancy could allow for the early detection of emerging deteriorations in maternal health. Autonomic modulation can be longitudinally and unobtrusively monitored by assessing heart rate variability (HRV). Yet, changes in maternal HRV (mHRV) throughout pregnancy remain poorly understood. In previous studies, mHRV is typically assessed only once per trimester with standard HRV features. However, since gestational changes are complex and dynamic, assessing mHRV comprehensively and more frequently may better showcase the changing autonomic modulation over pregnancy. Subsequently, we longitudinally (median sessions = 8) assess mHRV in 29 healthy pregnancies with features that assess sympathetic and parasympathetic activity, as well as heart rate (HR) complexity, HR responsiveness and HR fragmentation. We find that vagal activity, HR complexity, HR responsiveness, and HR fragmentation significantly decrease. Their associated effect sizes are small, suggesting that the increasing demands of advancing gestation are well tolerated. Furthermore, we find a notable change in autonomic activity during the transition from the second to third trimester, highlighting the dynamic nature of changes in pregnancy. Lastly, while we saw the expected rise in mean HR with gestational age, we also observed increased autonomic deceleration activity, seemingly to counter this rising mean HR. These results are an important step towards gaining insights into gestational physiology as well as tracking maternal health via mHRV.
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Bester et al. (2022) conducted an observational in Normal pregnancy (n=29). Longitudinal heart rate variability (HRV) monitoring vs. Early gestation (<23 weeks) was evaluated on Sample entropy (SampEn) at >32 weeks gestation compared to <23 weeks gestation (Cohen's U1 0.214, p=<0.0001). Advancing gestation in healthy pregnancies was associated with significant decreases in maternal vagal activity, heart rate complexity, and heart rate fragmentation.
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