title: Detection of a biorhythm of human fetal autonomic nervous activity by a power spectral analysis.
abstract: OBJECTIVE
  This study describes a 24-hour assay of autonomic nervous system activity in human fetuses with the use of a power spectral analysis of heartbeat intervals.
  
  
  METHODS
  The study included 6 normal fetuses and 11 growth-restricted fetuses, 3 of which were hypoxemic. Fetal heartbeats were continuously recorded for 24 hours, and a power spectral analysis was performed on the beat interval data. A low frequency domain of beat intervals was identified (0.025-0.125 cycles/beat) and evaluated at regular intervals over the 24-hour period. The cosinor method was used to detect rhythmic fluctuations in the resulting low frequency areas. The same procedures were also performed with the mothers of the fetuses.
  
  
  RESULTS
  We observed 2 diurnal rhythms of heartbeat activity (1 with a 12-hour period and another with a 24-hour period) in the normal and growth-restricted fetuses without hypoxemia. In contrast, these rhythms were not observed in the hypoxemic fetuses. In the mothers, only the 24-hour rhythm was observed.
  
  
  CONCLUSIONS
  The 12-hour cycle of autonomic nervous activity is present in normal fetuses.
authors.affiliation: Department of Obstetrics and Gynecology, Tohoku University Graduate School of Medicine, Sendai, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: Y
authors.initials: Y
authors.lastname: Kimura
authors.forename: J
authors.initials: J
authors.lastname: Murotsuki
authors.forename: T
authors.initials: T
authors.lastname: Murakami
authors.forename: S
authors.initials: S
authors.lastname: Uehara
authors.forename: K
authors.initials: K
authors.lastname: Okamura
mesh_terms: D001341:Autonomic Nervous System / Q000196:embryology*; D002940:Circadian Rhythm; D005260:Female; D005317:Fetal Growth Retardation / Q000503:physiopathology; D005323:Fetal Monitoring; D005333:Fetus / Q000502:physiology; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000196:embryology / Q000503:physiopathology; D011247:Pregnancy; D012016:Reference Values