3 . the Non - Invasive Assessment of Uterine Activity

The monitoring of uterine activity is of importance in prenatal medicine for the surveillance of the course of the pregnancy, and for assessing the condition of the fetus. The relevant information about uterine activity can be derived from mechanical effects, such as deformation, tension in the abdominal wall, changes in intrauterine pressure, and from electrical phenomena produced by the uterus, i.e. the muscle potentials which trigger the mechanical activity. Since the uterus is not readily accessible for the direct recording of the mechanical aspects of its activity, the results of such measurements, as performed clinically, provide only little information about the state of the uterus. Normally, the activity is evaluated in terms of the intrauterine pressure, usually in the form of the so-called tocogram. Two methods, one invasive and the other non-invasive, may be employed. For internal (invasive) tocography, the pressure is determined by introducing a catheter-tip pressure-transducer, or a catheter connected to an external transducer, into the uterine cavity. With this method, it is possible to determine the absolute intrauterine pressure. Often, however, internal tocography is not employed because of the practical difficulties involved. Moreover, the insertion of a catheter may stimulate parturition, so that this method may be contra-indicated for possible premature deliveries,