title: Fetal heart rate pattern interpretation in the second stage of labor using the five-tier classification: impact of the degree and duration on severe fetal acidosis.
abstract: OBJECTIVE
  The aim of this study was to clarify the association between fetal heart rate (FHR) tracing interpretation levels in the second stage of labor and poor fetal acid-base balance.
  
  
  METHODS
  The database at one tertiary hospital in Nagoya, Japan, was retrospectively reviewed for women with singleton fetuses in cephalic presentation and vaginal labor at ≥37 + 0 gestational weeks between 1 June 2011 and 30 April 2012. Continuous FHR tracings in the second stage of labor were subdivided into 15-min intervals, each of which we called a window, from the beginning of labor through delivery, and were assessed according to the five-tier classification proposed by the Japan Society of Obstetrics and Gynecology, in which level 1 is normal, level 2 is subnormal, and levels 3-5 are abnormal patterns.
  
  
  RESULTS
  In total, 777 parturient women were eligible for the study protocol. The numbers of women with maximal levels of 1, 2, 3, 4, and 5 were 3, 77, 341, 349, and 7, respectively. No cases of severe fetal acidosis (pH < 7.0 or base excess <-12 mmol/L) were recorded when the maximal levels were below 3. Both the pH and base excess of the umbilical artery decreased with higher levels of FHR tracings interpretation (P < 0.001). Both the summations of level-4 windows and level-3 and level-4 windows were significantly higher in women with severe fetal acidosis than in women without (P < 0.001), indicating that the duration of abnormal levels is associated with severe fetal acidosis.
  
  
  CONCLUSIONS
  Both the degree and duration of FHR tracing abnormalities correlate with severe fetal acidosis.
authors.affiliation: Department of Obstetrics and Gynecology, Japanese Red Cross Nagoya Daiichi Hospital, Nagoya, Japan.
authors.forename: Sayako
authors.initials: S
authors.lastname: Ikeda
authors.forename: Atsuko
authors.initials: A
authors.lastname: Okazaki
authors.forename: Ken
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Kana
authors.initials: K
authors.lastname: Kihira
authors.forename: Madoka
authors.initials: M
authors.lastname: Furuhashi
mesh_terms: D000138:Acidosis / Q000503:physiopathology*; D000328:Adult; D005260:Female; D005315:Fetal Diseases / Q000503:physiopathology*; D006340:Heart Rate, Fetal; D006801:Humans; D007748:Labor Stage, Second; D011247:Pregnancy; D013997:Time Factors
keywords: acid-base balance; fetal heart rate tracing; five-tier classification; second stage of labor; severe acidosis