Purpose of this thesis is to study the principle of operation of cardiotocography in monitoring fetal life, further defining the main requirements for this equipment and defining the parameters of monitored biosignals. These findings are supported by the literature. Based on the gained knowledge, the system design of cardiotocography is made with focus on reading contractions. Main parameters of the function blocks are defined. Circuit solution for sensing contractions is suggested, including the design of the sensor. Designed circuits are verified on a prototype.