Measuring the height of a cephalic presentation: an objective assessment of station.

The authors have previously described a method of objectively assessing the height of the presentation, an ultrasonic echograph measuring the distance from the head to the sacral tip. They have now obtained 453 measurements made before and during labor; norms are given according to the clinical evaluation of the station. The usefulness of the method is discussed. It may make the Bishop's score more precise, permit a more accurate check of trial of labor and help to recognize a low station correctly before an application of forceps.