title: Computerized analysis of normal fetal heart rate pattern throughout gestation.
abstract: OBJECTIVE
  To analyze the evolution of computerized cardiotocography (cCTG) parameters throughout gestation in a large archive of traces from healthy fetuses.
  
  
  METHODS
  This was a cross-sectional study of the first cCTG record from 4412 singleton fetuses with good pregnancy outcome. Normal ranges of cCTG parameters for 25 to 42 weeks were derived from analysis of only one cCTG record per fetus, and the relationship between the parameters and gestational age was investigated.
  
  
  RESULTS
  Fetal heart rate (FHR) accelerations, short- and long-term variation overall, duration of episodes of high and low variation and variation in high episodes increased with advancing gestation. In contrast, maternal perception of fetal movements, basal FHR, variation in low episodes and the time until criteria for normality were met decreased with advancing gestation. Gestational age-related changes in FHR variation were less evident at the lowest percentiles. Episodes of high FHR variation were detected in most fetuses, even at 25 weeks. Opposite trends of basal FHR and variation were observed at 42 weeks. Large decelerations and the frequency and duration of low episodes were also higher at 42 weeks.
  
  
  CONCLUSIONS
  The characteristics of the normal FHR pattern are quite defined from early on in gestation, follow a continuous trend with advancing gestation and change abruptly at 42 weeks. Gestational age-related changes are less obvious at the lowest percentiles.
authors.affiliation: Unidad de Medicina Materno-Fetal, Instituto Valenciano de Infertilidad, Universidad de Valencia, Valencia, Spain. Vicente.Serra-Serra@uv.es
authors.forename: V
authors.initials: V
authors.lastname: Serra
authors.forename: J
authors.initials: J
authors.lastname: Bellver
authors.forename: M
authors.initials: M
authors.lastname: Moulden
authors.forename: C W G
authors.initials: CW
authors.lastname: Redman
mesh_terms: D015148:Cardiotocography / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D049451:Nomograms; D011247:Pregnancy; D011256:Pregnancy Outcome; D016216:Ultrasonography, Prenatal