title: Power spectrum analysis of fetal heart rate variability at near term and post term gestation during active sleep and quiet sleep.
abstract: BACKGROUND
  Spectral analysis of fetal heart rate variability is promising for assessing fetal condition. Before using spectral analysis for fetal monitoring it has to be determined whether there should be a correction for gestational age or behavioural state.
  
  
  OBJECTIVE
  Compare spectral values of heart rate variability between near term and post term fetuses during active and quiet sleep.
  
  
  METHODS
  Case-control. Cases had a gestational age of > or =42 weeks; controls were 36 to 37 weeks. Fetuses were matched for birth weight percentile.
  
  
  METHODS
  STAN registrations from healthy fetuses. For each fetus one 5-minute segment was selected during active and one during quiet sleep.
  
  
  METHODS
  Absolute and normalized low (0.04-0.15 Hz) and high frequency power (0.4-1.5 Hz) of heart rate variability.
  
  
  RESULTS
  Twenty fetuses were included. No significant differences were found between cases and controls in absolute (481 and 429 respectively, P=0.88) or normalized low (0.78 and 0.80 respectively, P=0.50) or absolute (41 and 21 respectively, P=0.23) or normalized high frequency power (0.08 and 0.07 respectively, P=0.20) during active state. During rest, normalized low frequency power was lower (0.58 and 0.69 respectively, P=0.03) and absolute (16 and 10 respectively, P=0.04) and normalized high frequency power were higher (0.21 and 0.14 respectively, P=0.01) in cases compared to controls. Absolute and normalized low frequency power were higher during active state compared to rest in both groups (all P values <0.05).
  
  
  CONCLUSIONS
  We found sympathetic predominance during active state in fetuses around term. Post term parasympathetic modulation during rest was increased compared to near term.
authors.affiliation: Department of Obstetrics and Gynecology, Máxima Medical Centre, De Run 4600, 5504 DB, Veldhoven, The Netherlands. joehvanlaar@hotmail.com
authors.forename: J O E H
authors.initials: JO
authors.lastname: van Laar
authors.forename: C H L
authors.initials: CH
authors.lastname: Peters
authors.forename: R
authors.initials: R
authors.lastname: Vullings
authors.forename: S
authors.initials: S
authors.lastname: Houterman
authors.forename: S G
authors.initials: SG
authors.lastname: Oei
mesh_terms: D016022:Case-Control Studies; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005323:Fetal Monitoring / Q000379:methods; D005324:Fetal Movement / Q000502:physiology; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D007233:Infant, Postmature / Q000502:physiology*; D008297:Male; D011247:Pregnancy; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology*; D013057:Spectrum Analysis / Q000379:methods*; D047929:Term Birth / Q000502:physiology*; D016216:Ultrasonography, Prenatal / Q000379:methods