ABSTRACT: Ultrasound was initially developed as a submarine detection method in World War I. In the mid-1950s Ian Donald adapted the sonar device to scan for abdominal tumors, many of which turned out to be pregnancies. By 1965 fetal biparietal diameter and blighted ova were being detected by the technique, which had become a routine method for estimating fetal growth and maturity in many hospitals by 1968, although randomized controlled trials of safety and efficacy were still lacking. Although such trials are now being conducted and we await the results, a danger of technologies like ultrasound is that they substitute objective, partial knowledge of the patient's condition for patient-generated data. In addition, the process of obtaining technology-generated data diminishes the social relationships of patients and caregivers in several ways.