ANTEPARTUM COMPUTERIZED FETAL HEART-RATE, CHAOS ANALYSIS, BLOOD-GASES, AND PERINATAL OUTCOME

Objective: To investigate the role of chaos analysis in fetal heart ra te intervals for the differentiation of normal, suspicious, and abnorm al tracings. Methods: We plotted a quantitative graphic analysis of fe tal heart rate interval differences using the technique of phase-state analysis, commonly known as ''chaos.'' A computer disc containing 122 computerized fetal heart rate recordings from 21 pregnant women was s ent by one of the investigators, Geoffrey Dawes. No clinical informati on was given. Chaos plots were done and classified as normal, abnormal , and suspicious. The results were sent to Professor Dawes, who then p rovided the clinical data. Multiple correlative analyses were done on the classification of the computer calculation of fetal heart rate ind ices, blood gases, perinatal outcome, and chaos classification. Result s: Nineteen of the 21 fetuses had suspicious or abnormal long-term var iations of less than 30 msec. The average variation for the group was 18.2 msec. There was an average deceleration rate of 2.7 +/- 3.3/h. Th e average pH and base deficit was 7.2 +/- 0.1 and 6.5 +/- 4.5, respect ively. There were two stillbirths and one early perinatal death. Chaos plots forecast all deaths. A short-term variation of less than 2.9 ms ec was associated with death or acidemia in 5/6 cases. Conclusions: Ch aos plots and short-term variation calculations were similar in identi fying the fetus who is most ill. Both techniques emphasize that near-t erminal illness is associated with a loss of the regulatory interactio n between the heart and afferent stimuli from the nervous system.