Inter-observer reliability of 4 fetal heart rate classifications.

Objective: Different classification of fetal heart rate (FHR) pattern have been proposed: FHR classified as either "reassuring" or "non-reassuring", the National Institute of Child Health and Human Development (NICHD) published in 2008 a 3-tier system, the French College of Gynecology and Obstetrics (CNGOF) recommended in 2013 a 5-tier system and recently in 2015, the Federation International of Gynecology and Obstetrics (FIGO) proposed a new classification based on a 3-tier system. Our objective was to assess the inter-observer reliability of these 4 existing classifications.

Study Design: Four observers reviewed 100 FHR without clinical information. FHR were obtained from term singleton pregnancies. Fetal heart rate patterns were classified by one 2-tier ("reassuring vs. non-reassuring"), two 3-tier (NICHD 2008 and FIGO 2015), and one 5-tier (CNGOF 2013) fetal heart classifications.

Results: The global agreement between observers was moderate for each classification: 0.58 (0.40-0.74) for the 2-tier, 0.48 (0.37-0.58) for the NICHD 2008, 0.58 (0.53-0.63) for the CNGOF 2013 and 0.59 (0.49-0.67) for the FIGO 2015 classification. When FHR was classified as reassuring, it was classified as normal in 85.5% for the NICHD 2008 and in 94.5% for the FIGO 2015. For the CNGOF 2013, 65.0% were classified as normal and 32.5% as quasi normal. There was strong concordance between FIGO category I and "reassuring" FHR (kappa=0.95).

Conclusion: Inter-observer agreement of FHR interpretation is moderate whatever the classification used. To evaluate the superior interest of one classification, it will be interesting to compare their impact on need of second line techniques and on neonatal outcome.