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Procedures: Ultrasound

General Introduction

Ultrasonography or ultrasound scanning involves the application of an ultrasound transducer on the area to be examined. The transducter is used to transmit high-frequency sound waves, which bounce off internal structures to produce an image that can be displayed and recorded.
There are different versions of ultrasound scanning that are used in pregnancy and to help diagnose certain gynaecological problems. These include a pregnancy ultrasound (pelvic ultrasound scanning or sonography), Doppler ultrasound and a transvaginal ultrasound (endovaginal ultrasound or ultrasonography).

Pregnancy Ultrasound

Description and Purpose

A pregnancy ultrasound, also known as pelvic ultrasound scanning or sonography, consists of high-frequency sound waves, which provide an image, a sonogram, similar to an X-ray. The sonogram shows the baby's entire body, organs, and the surrounding tissues. A pregnancy ultrasound is used for the following reasons:

Preparation and Procedure

If the test is performed early into the pregnancy (i.e. during the first trimester), the woman will be asked to drink a lot of fluids beforehand in order to have a full bladder. This is because the full bladder descends, thus allowing a better view of the uterus , as well as the fact that the fluid is a good medium for the transmission of sound waves.
Later in pregnancy, a full bladder is not necessary, since the amniotic fluid provides the medium, and the enlarged uterus not only pushes the bladder down but extends so that it lies directly against the abdomen.

During the procedure, gel is applied to the abdomen, and an ultrasound transducer (used to transmit high-frequency sound waves, which bounce back to produce an image that can be recorded on X-ray film) is moved across the abdomen. The image is relayed in real time to a screen, which the doctor observes (for the reasons stated above). The sonogram, can be printed on film or paper or recorded on videotape, to be examined more carefully later, although the doctor may analyse the scan immediately during the procedure. The whole procedure takes between 15 minutes and 1 hour, in general.
Advantages Disadvantages
  • It entails no exposure to X-ray radiation.
  • It's non-invasive.
  • It produces quick results.
  • It creates a moving image.
  • Less reliable than amniocentesis or CVs in diagnosing certain disorders, such as Down syndrome.
  • False-positive and false-negative results are possible.

For more complete and additional information on this technique, contact the source for this page.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. The Yale University School of Medicine Patient's Guide to Medical Tests, Barry L. Zaret M.D., Senior Editor, published by Houghton Mifflin. Online:

Other HON resources 
   From MedHunt

Ultrasound in Pregnancy
    From HONselect
     (def;articles & more)   

Ultrasonography, Prenatal

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Ultrasonography, Prenatal


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Contact Last modified: Oct 20 2004