Until ultrasonic technics became available, accurate measurement of the fetal head size in utero was not obtainable. Savage (1) and Mengert and Korkmas (2) were not satisfied with the adequacy of roentgenographic cephalometry, and Crichton (3), evaluating the accuracy and value of cephalopelvimetry, stressed the difficulty in arriving at precise roentgen biparietal diameter measurements. In 1961 Donald and Brown (4) published an article on the employment of ultrasound for measuring the size of the fetal head. Following their report several other authors, including Taylor et al. (5) and Anderson and Niswonger (6), used ultrasound for the determination of the biparietal diameter in utero and recorded results within 3 mm of the actual postnatal caliper measurements. The proved accuracy of the ultrasonic technic of cephalometry has served as a stimulus for other workers to adopt the procedure and utilize it as a supplement to current diagnostic x-ray studies. Experimental work has attested to the safety of ul...