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Ultrasound examination during pregnancy.

Ultrasound examination during pregnancy.

Credits:N. Durrell McKenna, Wellcome Images

Ultrasound is a diagnostic imaging technology. It uses high-frequency sound waves - well beyond the range of human hearing - to produce pictures of the inside of the body. Ultrasound has many medical uses, but it is associated with screening pregnancies. This is because the technology is widely available and does not endanger the developing foetus.

Ultrasound scanners use a hand-held device called a transducer to scan the body. Crystals in the transducer send high-frequency sound waves into the body and detect the returning echoes. This is called the piezoelectric effect, which was discovered by Pierre Curie in 1880. A computer processes this information and produces a real-time moving image of the inside of the body.

During the Second World War the Allies developed sonar technology to detect underwater German U-boats. This relied on sound pitched within the range of human hearing. After the war, sound detection techniques were used for medical diagnosis and therapy. The higher the frequency of the sound, the smaller the objects that could be detected.

Ultrasound’s imaging potential was only realised in the late 1950s. Ian Donald experimented with ultrasound to picture internal organs, tumours and cysts. His Diasonograph ultrasound machine diagnosed gynaecological problems.

It took until the 1970s for ultrasound scanners to be commonly used in hospitalsEpidemiologist Alice Stewart’s studies found they were much safer than X‑rays for picturing foetuses. An ultrasound image of an unborn baby is now considered fundamental to the childbirth experience. Since 1972, ultrasounds which reveal serious fetal health problems have created decisions and dilemmas for parents. Termination of the pregnancy may be suggested, but this may be unacceptable to parents.


I Donald, J MacVicar, T G Brown, ‘Investigation of abdominal masses by pulsed ultrasound’, Lancet, 1 (1958), pp 1184-1194

R Bud and D J Warner (eds), Instruments of Science, An Historical Encyclopedia (London: Science Museum, 1998)

J van Dijck, The transparent body: a cultural analysis of medical imaging (Seattle; London: University of Washington Press, 2005)

B Holtzmann-Kevles, Naked to the Bone: Medical Imaging in the Twentieth Century (New Jersey: Rutgers University Press, 1997)

E M Tansey and D A Christie, Looking at the unborn: historical aspects of obstetric ultrasound a Witness Seminar held at the Wellcome Institute for the History of Medicine, London, on 10 March 1998

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S Blume, Insight and industry: on the dynamics of technological change in medicine (Massachusetts: MIT press, 1992)



The condition of having a developing unborn embryo or foetus in the body. A human pregnancy is usually of 40 weeks gestation.


The name given to the embryo during the later stages of development. In human reproduction it refers to an unborn child from its eighth week of development.


A method used to detect objects underwater by sending high frequency sound waves and monitoring their reflection.


A branch of medicine dealing with the treatment of disorders affecting the female reproductive system.


The study of epidemic disease, including its spread, causes and methods of control.