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Updated: May 4, 2026
Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings
Published on: October 25, 2015
Preterm birth has sex-specific effects on autonomic modulation of heart rate variability in adult sheep
Mary Berry1, Anne Jaquiery2, Mark Oliver3
1Liggins Institute, University of Auckland, Auckland, New Zealand.
Insights
Preterm birth alters cardiac autonomic activity in adult male sheep, potentially increasing cardiovascular risk. Gestational age impacts autonomic function in a sex-specific manner, even within the term range.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Regulation
- Perinatal Medicine
Background:
- Preterm birth affects 11% of infants globally, increasing their risk of adult cardiovascular disease.
- The mechanisms linking preterm birth to later cardiovascular issues are not fully understood.
- Altered cardiac autonomic activity, with increased sympathetic and/or reduced parasympathetic tone, may be a precursor to cardiovascular disease.
Purpose of the Study:
- To examine how gestational age influences cardiac autonomic activity in sheep offspring.
- To investigate potential sex-specific differences in these effects.
Main Methods:
- Sheep were randomized to spontaneous term birth (TC) or corticosteroid-induced preterm birth (PT).
- Cardiac autonomic modulation was assessed using heart rate variability (HRV) analysis in juvenile and adult offspring.
- Specific HRV parameters (LFnu, LogLF/HF, LogRMSSD, LogNN50) were analyzed.
Main Results:
- Preterm birth in adult male sheep showed altered sympatho-vagal balance (increased LFnu, LogLF/HF) and reduced parasympathetic activity (decreased LogRMSSD, LogNN50).
- In females, longer gestational age within the term range correlated with decreased LFnu in juveniles.
- In adult females, longer gestational age correlated with decreased LFnu and LF/HF ratio but increased RMSSD and NN50.
Conclusions:
- Gestational age at birth significantly impacts cardiac autonomic function in adult sheep, with sex-specific effects.
- These alterations in autonomic control may contribute to the elevated cardiovascular morbidity observed in individuals born preterm.
Introduction:
Globally, 11% of infants are born preterm. In adulthood, individuals born preterm are at increased risk of cardiovascular morbidity and mortality, but the mechanistic basis of this remains unknown. Clinically overt cardiovascular disease may be preceded by altered cardiac autonomic activity characterised by increased sympathetic activity and/or reduced parasympathetic activity. Thus, altered cardiac autonomic activity in survivors of preterm birth may underlie later cardiovascular risk.
Objective:
To investigate the impact of gestational age on cardiac autonomic activity in juvenile and adult sheep.
Methods And Results:
Singleton-bearing ewes were randomised antenatally to spontaneous term birth (TC; n=73) or corticosteroid induced preterm birth (PT; n=60). Cardiac autonomic modulation was assessed using heart rate variability analysis in juvenile and adult offspring. Preterm birth in adult males was associated with altered sympatho-vagal modulation (LFnu: PT 64 ± 4 vs. TC 49 ± 4, p<0.05; LogLF/HF: PT 1.8 ± 0.1 vs. TC 1.5 ± 0.1, p<0.05) and reduced parasympathetic modulation (LogRMSSD: PT 2.9 ± 0.2 vs. TC 3.4 ± 0.1, p<0.05; LogNN50: PT 0.3 ± 0.4 vs. TC 1.6 ± 0.4, p<0.05). Within the range of term birth, each one-day increment in gestational age was associated with a decrement in LFnu in juvenile females and with a decrement in LFnu and LF/HF ratio, but an increment in RMSSD and NN50 in adult females.
Conclusions:
Cardiac autonomic function in adult sheep is affected in a sex-specific manner by gestational age at birth, even within the term range. Altered cardiac autonomic function may contribute to increased later cardiovascular morbidity in those born preterm.
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