title: Quantitative comparison of entropy analysis of fetal heart rate variability related to the different stages of labor.
abstract: BACKGROUND
  The interpretation of the fetal heart rate (FHR) signal considering labor progression may improve perinatal morbidity and mortality. However, there have been few studies that evaluate the fetus in each labor stage quantitatively.
  
  
  OBJECTIVE
  To evaluate whether the entropy indices of FHR are different according to labor progression.
  
  
  METHODS
  A retrospective comparative study of FHR recordings in three groups: 280 recordings in the second stage of labor before vaginal delivery, 31 recordings in the first stage of labor before emergency cesarean delivery, and 23 recordings in the pre-labor before elective cesarean delivery.
  
  
  METHODS
  The stored FHR recordings of external cardiotocography during labor.
  
  
  METHODS
  Approximate entropy (ApEn) and sample entropy (SampEn) for the final 2000 RR intervals.
  
  
  RESULTS
  The median ApEn and SampEn for the 2000 RR intervals showed the lowest values in the second stage of labor, followed by the emergency cesarean group and the elective cesarean group for all time segments (all P<0.001). Also, in the second stage of labor, the final 5 min of 2000 RR intervals had a significantly lower median ApEn (0.49 vs. 0.44, P=0.001) and lower median SampEn (0.34 vs. 0.29, P<0.001) than the initial 5 min of 2000 RR intervals.
  
  
  CONCLUSIONS
  Entropy indices of FHR were significantly different according to labor progression. This result supports the necessity of considering labor progression when developing intrapartum fetal monitoring using the entropy indices of FHR.
authors.affiliation: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Jongil
authors.initials: J
authors.lastname: Lim
authors.affiliation: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Kwon
authors.affiliation: Department of Biostatistics, Scott & White Health Care, TX, USA; Department of Medicine, Texas A&M Health Science Center, TX, USA.
authors.forename: Juhee
authors.initials: J
authors.lastname: Song
authors.affiliation: Institute for Regenerative Medicine, Texas A&M Health Science Center, TX, USA.
authors.forename: Hosoon
authors.initials: H
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Jong Chul
authors.initials: JC
authors.lastname: Shin
authors.affiliation: Department of Obstetrics and Gynecology, The Catholic University of Korea, Seoul, South Korea. Electronic address: ooooobbbbb@catholic.ac.kr.
authors.forename: In Yang
authors.initials: IY
authors.lastname: Park
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D019277:Entropy; D005260:Female; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D007748:Labor Stage, Second / Q000502:physiology*; D011247:Pregnancy; D013997:Time Factors
keywords: Approximate entropy; Cardiotocography; Fetal heart rate; Labor progression; Sample entropy