title: Human fetal heart rate variability-characteristics of autonomic regulation in the third trimester of gestation.
abstract: OBJECTIVE
  To describe developmental aspects of the sympatho-vagal heart rate regulation in the human fetus by applying numerics to visual descriptions of fetal heart rate patterns throughout the third trimester of pregnancy. The focus is to determine potential benefits of this alternative means of assessing the maturation of the fetal autonomic nervous system by analysis of fetal heart rate variability (fHRV).
  
  
  METHODS
  The magnetocardiograms of 103 normal fetuses between 24+1 and 41+6 weeks of gestation were studied. Fetal heart beat intervals were determined with a temporal precision of 1 ms. The levels of fetal activity were estimated according to characteristic heart rate patterns (I-III) prior to 32, between 32-35 and beyond 35 (groups 1-3) completed weeks. Mean heart rate (mHR), standard deviation of normal-to-normal beat intervals (SDNN) and root mean square of successive differences of normal beats (RMSSD) served as fHRV indices, mean permutation entropy (PE_Mean) as complexity measure. SDNN/RMSSD was introduced as a potential marker for sympatho-vagal balance.
  
  
  RESULTS
  Low activity fHRP (I) were characterized by significantly lower level fHRV indices and higher PE_Mean when compared to fHRP II. We found that SDNN/RMSSD decreases with gestation in fHRP I, which suggests increasing vagal influence. In fHRP III (assigned to active awake fetuses only after 32 weeks), highest level SDNN and mHR are associated with a dramatically reduced complexity. fHRV indices cluster characteristically with the activity levels.
  
  
  CONCLUSIONS
  We conclude that a combined analysis of fHRV, based on SDNN/RMSSD and PE_Mean, and fHRP is advantageous in the assessment of maturation of the fetal autonomic nervous system.
authors.affiliation: University Hospital, Department of Obstetrics, Friedrich Schiller University of Jena, Germany. Uwe.Schneider@med.uni-jena.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Schneider
authors.forename: Birgit
authors.initials: B
authors.lastname: Frank
authors.forename: Anja
authors.initials: A
authors.lastname: Fiedler
authors.forename: Christiane
authors.initials: C
authors.lastname: Kaehler
authors.forename: Dirk
authors.initials: D
authors.lastname: Hoyer
authors.forename: Mario
authors.initials: M
authors.lastname: Liehr
authors.forename: Jens
authors.initials: J
authors.lastname: Haueisen
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Schleussner
mesh_terms: D001341:Autonomic Nervous System / Q000196:embryology / Q000502:physiology*; D005260:Female; D005324:Fetal Movement / Q000502:physiology; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D053798:Magnetocardiography; D011247:Pregnancy; D011263:Pregnancy Trimester, Third