An improvement of the acoustic fetal heart rate monitoring using statistical evaluation of the abdominal signal.

: An improved acoustical method for fetal heart rate (FHR) measurement is presented. The beat identification is based on the selection of the power peaks measured on two frequency channels. The identification of the valid peaks will be accomplished by rules, considering the timing and the amplitudes of the detected peaks with preferred search for pairs of the first and second sound. The introduced certainty factor as a function of the statistical probabilities that are related to the expected peaks, provides the reliability of the determined repetition time. Under a given certainty the result will be ignored and the FHR curve will be extended or left blank. The simplifications in the algorithms of the process reduce the required power consumption that enables its implementation in a low-power microcircuit and in this way to produce a battery-operated portable CTG instrument for long-term FHR monitoring on a passive.