An ultrasound imaging system is provided in which skin contact electrodes (210) are formed on the same substrate as an array of transducer elements. Skin impedance measurement is performed using the skin contact electrodes and the skin impedance is analyzed over time to determine a pain or discomfort level of the subject. This information may be used to adapt the imaging process (e.g. the position of the imaging system on the skin of a subject and the pressure applied) thereby to reduce discomfort.