title: Fetal autonomic response to severe acidaemia during labour.
abstract: OBJECTIVE
  Spectral analysis of heart-rate variability is used to monitor autonomic nervous system fluctuations. The low-frequency component is associated with sympathetic and parasympathetic modulation and the high-frequency component is associated with parasympathetic modulation. The objective was to study whether changes in low-frequency or high-frequency power of heart-rate variability occur in case of fetal distress.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  Obstetric unit of a tertiary-care teaching hospital.
  
  
  METHODS
  Twenty healthy human fetuses during labour at term of which ten had an umbilical artery pH < 7.05 (cases), and ten had an arterial pH > 7.20 (controls) after birth.
  
  
  METHODS
  Spectral information about fetal beat-to-beat heart rate, calculated from direct fetal electrocardiogram registrations, was obtained by using a short-time Fourier transform.
  
  
  METHODS
  Absolute power and normalised power in the low-frequency and high-frequency bands.
  
  
  RESULTS
  No differences were found between fetuses with and without acidaemia in absolute low or high frequency power (P = 0.2 and P = 0.3, respectively). During the last 30 minutes of labour, acidaemic fetuses had significantly increased normalised low-frequency power (P = 0.01) and decreased normalised high-frequency power (P = 0.03) compared with non-acidaemic fetuses. These differences were not observed from 3 to 2 hours before birth (P = 0.7 and P = 0.9, respectively).
  
  
  CONCLUSIONS
  The autonomic nervous system of human fetuses at term responds adequately to severe stress during labour. Normalised low and high frequency power of heart-rate variability might be able to discriminate between normal and abnormal fetal condition.
authors.affiliation: Department of Obstetrics and Gynaecology, Máxima Medical Centre, Veldhoven. 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: J W M
authors.initials: JW
authors.lastname: Bergmans
authors.forename: S G
authors.initials: SG
authors.lastname: Oei
mesh_terms: D000138:Acidosis / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000196:embryology*; D016022:Case-Control Studies; D036861:Delivery, Obstetric; D005316:Fetal Distress / Q000175:diagnosis* / Q000503:physiopathology; D005323:Fetal Monitoring / Q000379:methods / Q000592:standards; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013312:Stress, Physiological / Q000502:physiology