A simple pelvic diameter measurement can be performed with the patient in the supine position, measuring the distance from the outer edge of the anterior superior iliac spine on both sides, which is normally 23-25 cm, as well as the longest distance from the outer edge of the iliac crest on both sides, which is 25-28 cm. The distance from the midpoint of the pubic symphysis to the lower end of the spinous process of the 5th lumbar vertebra can also be measured with the patient in the lateral position, which is normally 28-20 cm. Finally, the distance between the medial sciatic tuberosities can be measured bilaterally, usually at 8-9.5 cm, which represents the transverse diameter of the sciatic tuberosities and the size of the pelvic outlet position.