title: Fetal heart rate variability during pregnancy, obtained from non-invasive electrocardiogram recordings.
abstract: OBJECTIVE
  Non-invasive spectral analysis of fetal heart rate variability is a promising new field of fetal monitoring. To validate this method properly, we studied the relationship between gestational age and the influence of fetal rest-activity state on spectral estimates of fetal heart rate variability.
  
  
  METHODS
  Prospective longitudinal study.
  
  
  METHODS
  Tertiary care teaching hospital.
  
  
  METHODS
  Forty healthy women with an uneventful singleton pregnancy.
  
  
  METHODS
  Non-invasive fetal electrocardiogram measurements via the maternal abdomen were performed at regular intervals between 14 and 40 weeks of gestation and processed to detect beat-to-beat fetal heart rate. Simultaneous ultrasound recordings were performed to assess fetal rest-activity state.
  
  
  METHODS
  Absolute and normalized power of fetal heart rate variability in the low (0.04-0.15 Hz) and high (0.4-1.5 Hz) frequency band were obtained, using Fourier Transform.
  
  
  RESULTS
  14% of all measurements and 3% of the total amount of abdominal data (330 segments) was usable for spectral analysis. During 21-30 weeks of gestation, a significant increase in absolute low and high frequency power was observed. During the active state near term, absolute and normalized low frequency power were significantly higher and normalized high frequency power was significantly lower compared with the quiet state.
  
  
  CONCLUSIONS
  The observed increase in absolute spectral estimates in preterm fetuses was probably due to increased sympathetic and parasympathetic modulation and might be a sign of autonomic development. Further improvements in signal processing are needed before this new method of fetal monitoring can be introduced in clinical practice.
authors.affiliation: Department of Obstetrics and Gynecology, Máxima Medical Centre, Veldhoven, the Netherlands.
authors.forename: Judith O E H
authors.initials: JO
authors.lastname: van Laar
authors.forename: Guy J J
authors.initials: GJ
authors.lastname: Warmerdam
authors.forename: Kim M J
authors.initials: KM
authors.lastname: Verdurmen
authors.forename: Rik
authors.initials: R
authors.lastname: Vullings
authors.forename: Chris H L
authors.initials: CH
authors.lastname: Peters
authors.forename: Saskia
authors.initials: S
authors.lastname: Houterman
authors.forename: Pieter F F
authors.initials: PF
authors.lastname: Wijn
authors.forename: Peter
authors.initials: P
authors.lastname: Andriessen
authors.forename: Carola
authors.initials: C
authors.lastname: van Pul
authors.forename: S
authors.initials: S
authors.lastname: Guid Oei
mesh_terms: D000328:Adult; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005323:Fetal Monitoring / Q000379:methods; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D011247:Pregnancy
keywords: Fetal monitoring; fetal electrocardiogram; fetal heart rate variability; frequency analysis; spectral analysis