title: Fetal heart rate monitoring of short term variation (STV): a methodological observational study.
abstract: BACKGROUND
  Cardiotocography (CTG) has high sensitivity, but less specificity in detection of fetal hypoxia. There is need for adjunctive methods easy to apply during labor. Low fetal heart rate short term variation (STV) is predictive for hypoxia during the antenatal period. The objectives of our study were to methodologically evaluate monitoring of STV during labor and to compare two different monitors (Sonicaid™ and EDAN™) for antenatal use.
  
  
  METHODS
  A prospective observational study at the obstetric department, Karolinska University hospital, Stockholm (between September 2011 and April 2015). In 100 women of ≥ 36 weeks gestation, STV values were calculated during active labor. In a subset of 20 women we compared STV values between internal and external signal acquisition. Additionally we compared antenatal monitoring with two different monitors in another 20 women.
  
  
  RESULTS
  Median STV in 100 fetuses monitored with scalp electrode during labor (EDAN™) was 7.1 msec (range 1.3-25.9) with no difference between early (3-6 cm) and late (7-10 cm) labor (7.1 vs 6.8 msec; p = 0.80). STV calculated from scalp electrode signals were positively correlated with delta-STV (STV internal -external) (R = 0.70; p < 0.01). No significant differences were found between Sonicaid™ and EDAN™ in antenatal external monitoring of STV (median difference 0.9 msec, Spearman Rank Correlation Sonicaid vs delta-STV; R = 0.35; p = 0.14).
  
  
  CONCLUSIONS
  Median intrapartum STV was 7.1 msec. Significant differences were found between internal and external signal acquisition, a finding that suggests further intrapartum studies to be analysed separately depending upon type of signal acquisition. Antenatal external monitoring with Sonicaid™ and EDAN™ indicates that the devices perform equally well in the identification of acidemic fetuses. Further studies are needed to assess the clinical value of intrapartum STV.
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden. stina.wretler@karolinska.se.
authors.forename: Stina
authors.identifier: http://orcid.org/0000-0001-9118-5036
authors.initials: S
authors.lastname: Wretler
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Holzmann
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden.|Department of Medicine, Centre for Pharmacoepidemiology, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Sophie
authors.initials: S
authors.lastname: Graner
authors.affiliation: Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Pelle
authors.initials: P
authors.lastname: Lindqvist
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden.
authors.forename: Susanne
authors.initials: S
authors.lastname: Falck
authors.affiliation: Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, 171 76, Stockholm, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Nordström
mesh_terms: D000328:Adult; D015148:Cardiotocography / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005311:Fetal Hypoxia / Q000175:diagnosis* / Q000517:prevention & control; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology; D007744:Obstetric Labor Complications / Q000175:diagnosis* / Q000517:prevention & control; D011247:Pregnancy; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
keywords: Cardiotocography; Computerized cardiotocography; Fetal heart rate; Fetal hypoxia; Fetal monitoring; Short term variation