The invention relates to determining a fetal heart rate from an ultrasonic Doppler echo signal, which comprises at least two channels, including a first channel obtained for a first depth range and a second channel obtained for a second depth range. A first heart rate is determined from the first channel (51, 53, 55) and a second heart rate is determined from the second channel (52, 54, 56). External information on the fetal heart rate and/or the maternal heart rate, extracted from an independent source (60, 61, 62) such as an ECG, is used to select one of the first heart rate and the second heart rate as the fetal heart rate to be determined. A preferred embodiment provides for elimination of double counting heart rates by cutting out unwanted signal contributions. The disclosure further provides for an adaptive signal processing and data acquisition controlled by patient related data.
