title: Complexity-loss in fetal heart rate dynamics during labor as a potential biomarker of acidemia.
abstract: BACKGROUND
  Continuous fetal heart rate (FHR) monitoring remains central to intrapartum care. However, advances in signal analysis are needed to increase its accuracy in diagnosis of fetal hypoxia.
  
  
  OBJECTIVE
  To determine whether FHR complexity, an index of multiscale variability, is lower among fetuses born with low (≤7.05) versus higher pH values, and whether this measure can potentially be used to help discriminate the two groups.
  
  
  METHODS
  Evaluation of a pre-existing database of sequentially acquired intrapartum FHR signals.
  
  
  METHODS
  FHR tracings, obtained from a continuous scalp electrocardiogram during labor, were analyzed using the multiscale entropy (MSE) method in 148 singletons divided in two groups according to umbilical artery pH at birth: 141 fetuses with pH>7.05 and 7 with pH≤7.05. A complexity index derived from MSE analysis was calculated for each recording.
  
  
  RESULTS
  The complexity of FHR signals for the last two hours before delivery was significantly (p<0.004) higher for non-acidemic than for acidemic fetuses. The difference between the two groups remained significant (p<0.003) when FHR data from the last 30min before delivery were excluded.
  
  
  CONCLUSIONS
  Complexity of FHR signals, as measured by the MSE method, was significantly lower for acidemic than non-acidemic fetuses. These results are consistent with previous studies showing that decreased nonlinear complexity is a dynamical signature of disrupted physiologic control systems. This analytic approach may have discriminative value in FHR analysis.
authors.affiliation: Division of Interdisciplinary Medicine and Biotechnology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA, USA. Electronic address: mcosta3@bidmc.harvard.edu.
authors.forename: Madalena D
authors.initials: MD
authors.lastname: Costa
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Schnettler
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, São João Hospital and Institute of Biomedical Engineering, University of Porto, Porto, Portugal.
authors.forename: Célia
authors.initials: C
authors.lastname: Amorim-Costa
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, São João Hospital and Institute of Biomedical Engineering, University of Porto, Porto, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Bernardes
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, São João Hospital and Institute of Biomedical Engineering, University of Porto, Porto, Portugal.
authors.forename: Antónia
authors.initials: A
authors.lastname: Costa
authors.affiliation: Division of Interdisciplinary Medicine and Biotechnology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA; The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA, USA.
authors.forename: Ary L
authors.initials: AL
authors.lastname: Goldberger
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, São João Hospital and Institute of Biomedical Engineering, University of Porto, Porto, Portugal.
authors.forename: Diogo
authors.initials: D
authors.lastname: Ayres-de-Campos
mesh_terms: D015148:Cardiotocography / Q000379:methods*; D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D007743:Labor, Obstetric; D008297:Male; D008661:Metabolism, Inborn Errors / Q000175:diagnosis*; D011247:Pregnancy
keywords: Cardiotocography; Complexity analysis; Fetal monitoring; Heart rate; Multiscale entropy