[Results and experiences with an autocorrelating ultrasonic cardiotocograph]

We present the results and experiences with a prototype cardiotocograph with US-autocorrelation processing. As this method is fundamentally different from conventional signal processing we are entering into the particular problems of this new FHR-technology. A total of 70 antepartum fetal rate recording from 53 patients and 38 intrapartum CTGs were evaluated. The antepartum results were excellent, the application time could be minimized and the quality of the recordings has been essentially improved. With the intrapartum recordings a computer comparison of long and short time irregularity of FHR derived from US-autocorrelation and direct fetal EKG was performed. The results proofed an excellent approximation to beat-to beat recording using the US-autocorrelation technique. The idea of using the new method intrapartum instead of invasive CTG could not be realised. This was due to a increasing loss of signal with progress of labor. To exclude maternal HR interferences the new monitor is supposed to record maternal heart rate simultaneously to FHR.