The recent article by Elliot et al presenting the association of neonatal metabolic acidosis and neurologic morbidity and the 5-color FHR classification of Parer and Ikeda deserves comment.

To understand the evolution of FHR patterns in association with adverse outcome, it would be important to know the category (normalcy) of each fetus both at the beginning of the labor as well as just before delivery. This would likely enable the authors to separate groups A (acidosis and encephalopathy) and I (acidosis only) according to problems arising during labor, during delivery, or previously. For this article, the analysis begins only 3 hours before delivery, without distinction of whether this time includes the first stage of labor or not. The authors present cumulative time (in 2-minute windows) in each color zone, although these brief times may not be consecutive or physiologically relevant. The average cumulative time in the red zone is brief (5.2–6.3 minutes), irrespective of outcome group. This suggests either rapid response to these patterns or, alternatively, that these patterns change rapidly. As the authors acknowledge, the timing and benefit of intervention, if any, is not included. The positive association between adverse outcomes beginning with the “blue and above” zone suggests a continuum of deterioration and a penalty for delay. It seems likely that the pattern of deterioration is probably as important as the cumulative duration at any color. Does the deteriorating fetus go sequentially from green to orange/red or can it jump colors? Can red or orange go to green and vice versa? And how rapidly?

About 25% of the encephalopathic group (A) had Apgars above 3 at 1 minute and above 6 at 5 minutes (Table 2), features that do not comport with “essential criteria” for assigning encephalopathy to the events of labor. Almost half (48.4%) of group A does not progress beyond the yellow zone, suggesting an unusually high false-negative (false-normal) rate. The study might profit from using low Apgar scores rather than base excess as the point of stratification. Low Apgar scores may have worse neurologic outcomes with “normal” pHs rather than “low” pHs. Finally, failure to recognize a benign pattern as the maternal heart rate may help to explain abnormal outcomes with apparently benign patterns.