INTRODUCTION: In obstetrics, monitoring of the fetus using CTG is now part of the accepted standard. Most commonly, the fetal heart rate is detected with a Doppler ultrasound transducer (ultrasonic cardiography). In some cases, however, a maternal signal is recorded instead of the child's heart rate. If the maternal heart rate is within a normal range for the fetus (around 130 bpm), the worst case scenario is that the incorrect measurement is not picked up and the recorded heart rate is not interpreted correctly. An asphyctic newborn or a stillbirth are the worst consequences of this avoidable error. However, if the maternal heart rate is also recorded (e.g. using pulsoxymetry or by recording a maternal ECG), concurrence of the two heart rates can be identified and the monitoring staff will be alerted (coincidence detection). In most cases, however, continuous monitoring of the maternal heart rate is omitted in the interests of the patient's comfort. MATERIALS AND METHODOLOGY: A new method of detecting coincidence was examined in this study. The maternal heart rate was measured with a modified tocography transducer (“abdominal pulse sensor”). The advantage of this approach is the incorporation of the measurement of the maternal heart rate into the tocography transducer that is already used during CTG. This means that coincidence analysis will always function without the need for additional cables or sensors. Philips GmbH has developed an “abdominal pulse sensor” for this, which measures the maternal heart rate using two infrared diodes installed in the base of the transducer. The heart rate is determined by photoplethysmography. This method is ideal for measuring the maternal heart rate, as, firstly, penetration of infrared light is not harmful to the fetus and, secondly, the sensor can be integrated into the existing setup used for CTG measurements. RESULTS: In a clinical feasibility study, the “abdominal pulse sensor” was tested on pregnant women 26 weeks or more into their pregnancy. It was demonstrated that the “abdominal pulse sensor” records the maternal heart rate with an acceptable degree of reliability. To this end, the quantity (proportion of actual “abdominal pulse sensor” readings compared to reference ECG readings) and the quality (proportion of “abdominal pulse sensor” readings with an absolute deviation from the ECG < 5 bpm) were determined as target variables. In the second series of measurements with the enhanced “abdominal pulse sensor”, an average reading quality of 96.7 % was achieved. The quantity was 84.2 %. CONCLUSION: On the basis of the data recorded to date, the new CTG system with built-in measurement of the maternal heart rate using the “abdominal pulse sensor” is reliably able to determine the maternal heart rate with a high degree of quality. If the quantity is sufficient, it offers additional safety when monitoring fetuses in utero with the same degree of comfort for the patient. This additional measurement could increase the safety of the unborn child.