Observer Variability in Assessment of Antepartum Cardiotocograms

Summary One hundred cardiotocograms (CTGs) were marked twice independently by five observers to assess the inter‐ and intra‐observer reliability of the interpretation of the antepartum CTG. Scores given for basal heart rate, variability expressed in terms of oscillatory amplitude and frequency, the presence of accelerations and decelerations were studied, as well as a total score combining these variables. Assessment of CTGs with this scoring system was compared to subjective assessment using two sets of criteria. Both inter‐ and intra‐observer reliability was higher with the scoring system than in the subjective assessments. The highest intra‐ and inter‐observer consistency in interpretation, was found for basal heart rate followed by decelerations. Oscillatory frequency was slightly more reliable than oscillatory amplitude. Accelerations were so unreliable that it war necessary to clearly define these in terms of both amplitude and duration. It is concluded that the interpretation of the antepartum CTG is not as easy nor as reproducible as one may wish. In this respect the scoring system, which is easy to use, offers major advantages when compared to subjective assessment.