title: Nonlinear analysis of fetal heart rate dynamics in fetuses compromised by asymptomatic partial placental abruption.
abstract: BACKGROUND
  We analyzed fetal heart rate (FHR) parameters, dynamics, and outcomes in pregnancies with asymptomatic partial placental abruption (PPA) compared with those in normal pregnancies.
  
  
  METHODS
  We examined nonstress test (NST) data acquired from 2003 to 2012 at our institution. Normal pregnancies (N = 170) and PPA cases (N = 17) were matched for gestational age, fetal sex, and mean FHR. NSTs were performed at 33-42 weeks of gestation. FHR parameters obtained from the NST and perinatal outcomes were analyzed using linear methods. Nonlinear indices, including approximate entropy (ApEn), sample entropy (SampEn), short-term and long-term scaling exponents (α1 and α2), and correlation dimension (CD), were used to interpret FHR dynamics and system complexity. The area under a receiver operating characteristic curve (AUC) was used to evaluate the nonlinear indices.
  
  
  RESULTS
  There were no significant differences in general characteristics and FHR parameters between the PPA and control groups. However, gestational age at delivery, birth weight, 5-min Apgar scores, ApEn, SampEn, and CD were significantly lower in the PPA group than in the control group (P < 0.05). The long-term scaling exponent (α2) and crossover index (α2/α1) of the PPA fetuses were significantly higher than those of the controls (P < 0.01). A multiple regression model showed better performance in predicting PPA (AUC, 0.92; sensitivity 82.35%; specificity, 94.12%).
  
  
  CONCLUSIONS
  Nonlinear dynamic indices of FHR in asymptomatic PPA were qualitatively different from those in normal pregnancies, whereas the conventional FHR parameters were not significantly different.
authors.affiliation: College of General Education, Hanbat National University, Daejeon, South Korea.
authors.forename: Won-Young
authors.initials: WY
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, College of Medicine, Hanyang University, Seoul, South Korea. Electronic address: hohjk@hanyang.ac.kr.
authors.forename: Jeong-Kyu
authors.initials: JK
authors.lastname: Hoh
mesh_terms: D000037:Abruptio Placentae / Q000503:physiopathology*; D000328:Adult; D005260:Female; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D008297:Male; D017711:Nonlinear Dynamics; D011247:Pregnancy; D055815:Young Adult
keywords: Approximate entropy; Correlation dimension; Fetal heart rate; Nonlinear dynamic indices; Partial placental abruption; Sample entropy; Short-term and long-term scaling exponents