We read with interest a recent article by Coletta and colleagues comparing the 3-tier system for fetal heart rate classification proposed by the Eunice Kennedy Shriver National Institute of Child Health and Human Development with a 5-tier color-coded system originally described by Parer and Ikeda. The authors concluded that the 5-tier system was more sensitive than the 3-tier system in the detection of acidemia. We propose a different interpretation of the data.

In the 5-tier system, the green, blue, and yellow tiers were statistically indistinguishable from one another in their ability to predict acidemia. The orange and red tiers were statistically different from the other 3 tiers but were identical to one another. Consequently, the 5-tier system effectively identified only 2 distinct tiers of risk for acidemia. Tracings that were outside the combined green, blue, and yellow category accurately identified 19 of 24 acidemic neonates (sensitivity 79%), whereas tracings outside category I accurately identified 23 of 24 acidemic neonates (sensitivity 96%). From this perspective, the sensitivity of the 5-tier system was not superior to the 3-tier system but instead was slightly inferior.

The authors reported that most of the tracings resulting in acidemia were category II and therefore had “no clearly defined management strategy.” Contrary to this notion, recent publications have described highly detailed management strategies for such tracings, including intrauterine resuscitative measures and, if not successful, consideration of delivery. Interestingly, these recommendations are identical to the management actions recommended for all tracings in the blue, yellow, and orange categories.

As the authors noted, further research is needed to refine the existing 3-tier system. However, the solution to an imperfect yet simple 3-tier system is not to replace it with a complex, cumbersome 5-tier system that does not identify 5 categories of risk and offers no new recommendations for management.