title: Multicentre study of fetal cardiac time intervals using magnetocardiography.
abstract: OBJECTIVE
  A database with reference values of the durations of the various waveforms in a magnetocardiogram of fetuses in uncomplicated pregnancies is assessed. This database will be of help to discriminate between pathologic and healthy fetuses. A fetal magnetocardiogram is a recording of the magnetic field in a location near the maternal abdomen and reflects the electric activity within the fetal heart. It is a non-invasive method, which can be used with nearly 100% reliability from the 20th week of gestation onward.
  
  
  METHODS
  Durations of the waveforms were assembled from averaged magnetocardiograms and statistically processed.
  
  
  METHODS
  Fetal magnetocardiograms were measured with different magnetocardiographs. All measurements were carried out in magnetically shielded rooms.
  
  
  METHODS
  Fetal magnetocardiograms were obtained for 582 healthy patients.
  
  
  METHODS
  The durations of the waveforms were extracted from fetal magnetocardiograms measured at the cooperating centres. The variables collected included the duration of the P-wave, the PR interval, the PQ interval, the QRS complex, the QT interval and the T-wave and QTc value. The results were compared with values extracted from electrocardiograms of fetuses measured via electrodes attached to the maternal abdomen, from electrocardiograms measured during labour using a scalp electrode, and from electrocardiograms recorded in newborns, that were found in the literature.
  
  
  METHODS
  Values of the durations are given as a function of gestational age including the regression line as well as the bounds marking the 90%, 95% and 98% prediction interval.
  
  
  RESULTS
  The durations of the P-wave, the PR interval, the QRS complex, the QT interval and QTc value increase linearly with gestational age. The durations of the PQ interval and the T-wave are independent of fetal age.
  
  
  CONCLUSIONS
  The values found agree with those found in the literature. The scatter of the data is wide due to the variation in normal physiology, the measuring system and signal processing and the subjectivity of the researcher. However, the system can define normal ranges and may be used in diagnosis.
authors.affiliation: Low-Temperature Division, University of Twente, Enschede, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Stinstra
authors.forename: E
authors.initials: E
authors.lastname: Golbach
authors.forename: P
authors.initials: P
authors.lastname: van Leeuwen
authors.forename: S
authors.initials: S
authors.lastname: Lange
authors.forename: T
authors.initials: T
authors.lastname: Menendez
authors.forename: W
authors.initials: W
authors.lastname: Moshage
authors.forename: E
authors.initials: E
authors.lastname: Schleussner
authors.forename: C
authors.initials: C
authors.lastname: Kaehler
authors.forename: H
authors.initials: H
authors.lastname: Horigome
authors.forename: S
authors.initials: S
authors.lastname: Shigemitsu
authors.forename: M J
authors.initials: MJ
authors.lastname: Peters
mesh_terms: D000704:Analysis of Variance; D015148:Cardiotocography / Q000379:methods*; D004562:Electrocardiography / Q000379:methods; D005318:Fetal Heart / Q000502:physiology*; D005865:Gestational Age; D006329:Heart Conduction System / Q000502:physiology; D006340:Heart Rate, Fetal; D006801:Humans; D008280:Magnetics; D012016:Reference Values; D013997:Time Factors