Toward quantitative monitoring of human cardiotocography during labor

Continuous monitoring of the fetal heart rate (FHR) during maternal labor is a very common practice, but improved outcome has been difficult to show. A possible reason is the qualitative nature of the interpretation of fetal heart rate records by clinical personnel. We aim to enhance the clinical utility of this practice by developing and implementing quantitative measures of abnormal features of fetal heart rate records. To quantify the timing and extent of heart rate changes during uterine contraction, we have adapted cross-correlation analysis. To quantify heart rate variability in the presence of missing data points, we have calculated the Lomb periodogram. To detect the co-existence of reduced variability and transient decelerations, we have calculated sample entropy. Here we describe the methods and give distributions of these measures for 69 courses of labor not requiring emergent surgical intervention.