Objective: Despite its routine use in intrapartum care, the technique of fetal cardiotocography has some limitations. The aim of this study is to analyze the predictive capacity and interobserver agreement in the latest versions of four international cardiotocography guidelines: Federation of Gynecology and Obstetrics (FIGO), American College of Obstetrics and Gynecology (ACOG), the National Institute for Health and Care Excellence (NICE) and Chandraharan, used to predict neonatal acidemia.
Study design: The last 30 min of 150 cardiotocographic records were analyzed over all the pH ranges and were blindly evaluated by three independent reviewers. The sensitivity, specificity, positive predictive value, negative predictive value, and area under the receiver operating characteristic curve (AUC) were calculated to assess the predictive capacity of each fetal cardiotocographic guideline. The degree of interobserver agreement was evaluated with the Fleiss Kappa coefficient.
Results: Observers found fetal cardiotocography guidelines to have a variable sensitivity and specificity. The Chandraharan classification reached the highest sensitivity (78.79%), while ACOG had the highest specificity (95.73%). On average for the three observers, Chandraharan had the highest discrimination capacity for neonatal acidemia, although this was only moderate (AUC 0.66; 95%CI, 0.55-0.77) and did not differ significantly from the remaining guidelines. The degree of agreement among the three observers, assessed according to the Fleiss Kappa coefficient, was generally acceptable or moderate for all items and classifications, being highest with the FIGO classification (ĸ = 0.35; 95%CI, 0.28-0.41) and lowest with the ACOG (ĸ = 0.23; 95%CI, 0.16-0.30).
Conclusion: Although all the guidelines have a moderate capacity to predict neonatal acidemia, the Chandraharan guideline has the highest capacity. This follows a different approach from the others in that it relies on interpretations of cardiotocographic traces based on fetal physiology. The degree of interobserver agreement is, in general, acceptable for the four guidelines, and is the highest for FIGO.
Keywords: Electronic fetal monitoring; cardiotocography; fetal physiology; interobserver agreement; neonatal academia.