Evaluation of fetal acidemia during delivery using the conventional 5-tier classification and Rainbow systems

Abstract

The association between prepartum time-series fetal heart rate pattern changes and cord blood gas data at delivery was examined using the conventional 5-tier classification and the Rainbow system for 229 female patients who delivered vaginally. They were classified into three groups based on the results of umbilical cord blood gas analysis at delivery. The fetal heart rate pattern classifications were based on analysis of measurement taken at 10-min intervals, beginning at 120 min pre-delivery. The relationship between fetal heart rate pattern classification and cord blood pH at delivery changed over time. The 5-tier classification at each interval increased before delivery in the Mild and Severe groups compared with the Normal group. No significant differences were observed between acidemia groups. The Rainbow classification showed a significant differences between the acidemia groups at each interval, particularly during the prepartum period. A relationship between classification and outcome was evident before delivery for both the 5-tier classification and Rainbow system.

Fig 1. CTG levels of each group before delivery in the conventional 5-tier classification and Rainbow system.

Circles indicate the level course of the Normal group, squares indicate that of the Mild group, and triangles indicate that of the Severe group. The transition was the average change in each group. #^, *, and † indicate the periods when there were significant differences between groups: # for Normal vs. severe, * for Normal vs. Mild, and † for Mild vs. Severe. A shows a group comparison of CTG levels using the conventional 5-tier classification. B shows a comparison of CTG levels using the Rainbow system.