title: Contribution of the fetal baroreceptor reflex to the low frequency component of fetal heart rate fluctuations.
abstract: OBJECTIVE
  The objective of this study was to examine whether the fetal baroreceptor reflex contributed to the low frequency component (LF: 0.025-0.125 cycles/beat) of fetal heart rate fluctuations.
  
  
  METHODS
  Sheep fetuses in late gestation with normoxemia were used. The baroreceptor function was expressed as the baroreceptor reflex sensitivity (BRS) based on the change of the R-R interval in response to the elevation of blood pressure by noradrenaline (Nor-Ad). A frequency analysis was conducted by the autoregression method on heart rate fluctuations and blood pressure fluctuations in 300 stable heart beats immediately before the Nor-Ad test. The gain and the coherence from blood pressure LF to heart rate LF were calculated. The correlations between the BRS and the power values of heart rate LF, blood pressure LF, and the gain or the coherence were examined.
  
  
  RESULTS
  The BRS and the gain showed a positive correlation (p < 0.01). There was a negative correlation between the heart rate LF and the BRS, and between the blood pressure LF and the BRS (p < 0.01, p < 0.005).
  
  
  CONCLUSIONS
  This study showed that fetal BRS was involved in the change of LF in fetal heart rate fluctuation. Baroreceptor function should be considered when examining the change of LF domain in fetal heart beat fluctuation.
authors.affiliation: Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Hisaya
authors.initials: H
authors.lastname: Suzuki
authors.forename: Junichi
authors.initials: J
authors.lastname: Sugawara
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Murakami
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Okamura
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal; D009638:Norepinephrine / Q000494:pharmacology; D011247:Pregnancy; D012756:Sheep / Q000196:embryology
chemical_list: D009638:Norepinephrine