title: Analysis of fetal heart rate variability obtained by magnetocardiography.
abstract: OBJECTIVE
  To obtain fetal magnetocardiogram (fMCG) recordings in preterm fetuses in both shielded and unshielded clinical settings.
  
  
  METHODS
  Seventeen fMCG recordings were obtained from 6 low-risk fetuses of 26-35 weeks' postmenstrual age. The superconducting quantum interference device biomagnetometer was positioned over the gravid abdomen, and the signals, associated with the bioelectrical activity of the fetal heart, were digitized at a sampling rate of 1 kHz. The fMCG signal was recorded for 5 minutes along with the reference maternal electrocardiogram in both the shielded and unshielded environment. A nonsyntactic QRS detection algorithm based on Pan-Tompkins scheme was employed for extracting fetal RR time series.
  
  
  RESULTS
  The growth rate of 1.97 decibels (dB) exhibited by the low-frequency (LF) band is almost 2 1/2 times that of the high-frequency (HF) band. HF/LF power ratio was calculated to have a negative growth rate of -0.17 dB/wk (P = .004). Total power increased at approximately 1.35 dB/wk (P = .031).
  
  
  CONCLUSIONS
  Consistent with the literature, the total power, or the variance, as well as the LF and HF powers independently, indicates an increasing trend with increasing postmenstrual age.
authors.affiliation: Department of Nursing Systems, School of Nursing, University of Texas Health Science Center at Houston, 77030, USA. M.T.Verklan@uth.tmc.edu
authors.forename: M Terese
authors.initials: MT
authors.lastname: Verklan
authors.forename: Nikhil S
authors.initials: NS
authors.lastname: Padhye
authors.forename: Audrius
authors.initials: A
authors.lastname: Brazdeikis
mesh_terms: D001341:Autonomic Nervous System / Q000502:physiology*; D047109:Fetal Development / Q000502:physiology; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D053798:Magnetocardiography; D013057:Spectrum Analysis