The study presented here relates a tissue hardness (stiffness) measurement system, or more precisely for example, external labor transducer for monitoring of gravidae, including possible cases of fetal and maternal combined signal transducer. As a theory of measurement, suction cup is applied on subject body surface where the tissue hardness thereon or shallow depth, is to be measured. Unlike conventional “pushing” type measurement, our method is to apply negative pressure (sucking) thereon by suction cup. Response of the body surface to this negative pressure is measured for external labor for example. The advantage of this method is that the suction cup can hold it on body surface for itself, to allow belt-less labor (and fetal signal by the way) transducer, for easier operation.