Measuring cervical dilatation in human parturition using the Hall effect.

An instrument was developed to continuously measure cervical dilatation in human labor. The instrument utilizes a small magnetic field source, which is attached to one edge of the cervix while a magnetic field sensor is attached to the diametrically opposite edge of the cervix. The sensor, using two Hall generators, measures orthogonal components of the field to minimize the effects of angular orientation between the source and sensor. The instrument's characteristics indicate that it can measure dilation throughout the range of 1-10 cm, but because its clinical reliability is consistent from only 1-7 cm, the equipment needs to be improved in the ways outlined in the text. This measurement, especially when analyzed with the continous measurement of intrauterine pressure, can provide the obstetrician with new insight into the physiology of labor.