Simple instrument for measuring cervical dilatation during labour

The construction of a simple disposable instrument for the measurement of cervical dilatation is described. The instrument consists of two clips, a measuring tape and a flexible tube. The measuring tape is fixed to one clip and threaded through the flexible tube, which is fixed to the other clip. The clips are attached to opposing cervical rims at 3 o'clock and 9 o'clock and the differential displacement of the marking on the measuring tape and free end of the flexible tube is measured. Laboratory measurements were performed in order to determine the error of measurement. The absolute error of measurement with this instrument is 1.5 mm. Clinical measurements were performed on 12 parturients with a single foetus in vertex position and 3 to 4 cm cervical dilatation. The results of measurements were within +/-1 cm error margin of manual assessments. No adverse effects were noted due to the use of the instrument. The instrument did cause minor discomfort to patients during application.