Subspace detection of the impulse response function from intrapartum uterine pressure and fetal heart rate variability

Using clinically measured intrapartum cardiotocography (CTG) data, the objective of this study was to detect the impulse response function (IRF) of the single-input single-output system composed of uterine pressure as the input and one of three frequency band powers of fetal heart rate variability (fHRV) as the output. The results showed statistically significant differences between normal fetuses and those that had developed metabolic acidosis. This occurred in all frequency bands, with more differences occurring in the higher bands. These results are very promising for the improved detection of fetal distress related to hypoxia.