title: Swedish randomized controlled trial of cardiotocography only versus cardiotocography plus ST analysis of fetal electrocardiogram revisited: analysis of data according to standard versus modified intention-to-treat principle.
abstract: OBJECTIVE
  To undertake a renewed analysis of data from the previously published Swedish randomized controlled trial on intrapartum fetal monitoring with cardiotocography (CTG-only) vs. CTG plus ST analysis of fetal electrocardiogram (CTG+ST), using current standards of intention-to-treat (ITT) analysis and to compare the results with those of the modified ITT (mITT) and per protocol analyses.
  
  
  METHODS
  Renewed extraction of data from the original database including all cases randomized according to primary case allocation (n=5 049).
  
  
  METHODS
  Metabolic acidosis in umbilical artery at birth (pH <7.05, base deficit in extracellular fluid >12.0 mmol/l) including samples of umbilical vein blood or neonatal blood if umbilical artery blood was missing.
  
  
  RESULTS
  The metabolic acidosis rates were 0.66% (17 of 2 565) and 1.33% (33 of 2 484) in the CTG+ST and CTG-only groups, respectively [relative risk (RR) 0.50; 95% confidence interval (CI) 0.28-0.88; p=0.019]. The original mITT gave RR 0.47, 95%CI 0.25-0.86 (p=0.015), mITT with correction for 10 previously misclassified cases RR 0.48, 95%CI 0.24-0.96 (p=0.038) and per protocol analysis RR 0.40, 95%CI 0.20-0.80 (p=0.009). The level of significance of the difference in metabolic acidosis rates between the two groups remained unchanged in all analyses.
  
  
  CONCLUSIONS
  Re-analysis of data according to the ITT principle showed that regardless of the method of analysis, the Swedish randomized controlled trial maintained its ability to demonstrate a significant reduction in metabolic acidosis rate when using CTG+ST analysis for fetal surveillance in labor.
authors.affiliation: Department of Women and Child Health, Karolinska Institute, Stockholm, Sweden.
authors.forename: Isis
authors.initials: I
authors.lastname: Amer-Wåhlin
authors.forename: Ingemar
authors.initials: I
authors.lastname: Kjellmer
authors.forename: Karel
authors.initials: K
authors.lastname: Maršál
authors.forename: Per
authors.initials: P
authors.lastname: Olofsson
authors.forename: Karl Gustaf
authors.initials: KG
authors.lastname: Rosén
mesh_terms: D015148:Cardiotocography / Q000379:methods*; D036861:Delivery, Obstetric / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D033182:Intention; D057194:Intention to Treat Analysis; D007743:Labor, Obstetric; D011247:Pregnancy; D011256:Pregnancy Outcome; D013548:Sweden