title: Monitoring fetal electrocortical activity during labour for predicting worsening acidemia: a prospective study in the ovine fetus near term.
abstract: BACKGROUND
  Severe fetal acidemia during labour with arterial pH below 7.00 is associated with increased risk of hypoxic-ischemic brain injury. Electronic fetal heart rate (FHR) monitoring, the mainstay of intrapartum surveillance, has poor specificity for detecting fetal acidemia. We studied brain electrical activity measured with electrocorticogram (ECOG) in the near term ovine fetus subjected to repetitive umbilical cord occlusions (UCO) inducing FHR decelerations, as might be seen in human labour, to delineate the time-course for ECOG changes with worsening acidemia and thereby assess the potential clinical utility of fetal ECOG.
  
  
  RESULTS
  Ten chronically catheterized fetal sheep were studied through a series of mild, moderate and severe UCO until the arterial pH was below 7.00. At a pH of 7.24 ± 0.04, 52 ± 13 min prior to the pH dropping <7.00, spectral edge frequency (SEF) increased to 23 ± 2 Hz from 3 ± 1 Hz during each FHR deceleration (p<0.001) and was correlated to decreases in FHR and in fetal arterial blood pressure during each FHR deceleration (p<0.001).
  
  
  CONCLUSIONS
  The UCO-related changes in ECOG occurred in advance of the pH decreasing below 7.00. These ECOG changes may be a protective mechanism suppressing non-essential energy needs when oxygen supply to the fetal brain is decreased acutely. By detecting such "adaptive brain shutdown," the need for delivery in high risk pregnant patients may be more accurately predicted than with FHR monitoring alone. Therefore, monitoring fetal electroencephalogram (EEG, the human equivalent of ECOG) during human labour may be a useful adjunct to FHR monitoring.
authors.affiliation: Department of Obstetrics and Gynecology, Lawson Health Research Institute, The University of Western Ontario, London, Ontario, Canada. mg.frasch@umontreal.ca
authors.forename: Martin G
authors.initials: MG
authors.lastname: Frasch
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Keen
authors.forename: Robert
authors.initials: R
authors.lastname: Gagnon
authors.forename: Michael G
authors.initials: MG
authors.lastname: Ross
authors.forename: Bryan S
authors.initials: BS
authors.lastname: Richardson
mesh_terms: D000138:Acidosis / Q000175:diagnosis* / Q000196:embryology* / Q000503:physiopathology; D000818:Animals; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D005260:Female; D005323:Fetal Monitoring / Q000379:methods*; D005324:Fetal Movement / Q000502:physiology*; D005333:Fetus / Q000503:physiopathology*; D005740:Gases / Q000097:blood; D006321:Heart / Q000503:physiopathology; D006340:Heart Rate, Fetal / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007743:Labor, Obstetric / Q000502:physiology*; D008297:Male; D010100:Oxygen; D011247:Pregnancy; D034561:Sheep, Domestic
chemical_list: D005740:Gases; D010100:Oxygen