Ultrasound produces detailed pictures of the body in real-time using high frequency sound waves, which are produced by a special ultrasound probe, called a transducer. The frequency of these sound waves is higher than that detected by the human ear and when they are reflected by a part of the body they are detected by the probe and are used to create images that can be displayed on a monitor. Because they are captured in real time they appear as moving images not as static or still ones, thus enhancing the diagnostic capability of the test. Ultrasound is a safe and widely used imaging technique. It has no known harmful effects and can be used to image a variety of conditions including pregnancy, gallstones and varicose veins. Ultrasound can also be used to measure blood flow through vessels, when it is called a colour flow Doppler or Duplex scan.
Pregnancy ultrasounds may be performed by examination of the abdomen called transabdominal or by using a special probe designed to be inserted into the vagina, called transvaginal. The type of examination you will need will depend on what your referring doctor has requested and the nature of the clinical condition being investigated.
Who will be Performing the Scan?
Your examination or scan will be performed by either a sonographer (a specially trained technologist) or a Radiologist (a highly trained specialist doctor). Because the examiner is interpreting many moving images on a screen, a high degree of concentration is required to obtain accurate information. Therefore, in most circumstances except obstetric scans, family and friends of the patient are not generally permitted to watch the procedure. If you have accompanying children you will have to bring along someone to watch them during your examination.
Early Pregnancy Scan
- Finish drinking 1 litre of water 1 hour prior to exam.
- Do not empty bladder.
- Continue to take any current medication
Anatomy Pregnancy Scan
- Drink 2 glasses of water half an hour prior to your appointment
- Do not empty bladder
- Continue to take any current medication.
For most ultrasound examinations you will be required to change into a gown and lie on an examination couch. You will remain covered during your examination except for the area being imaged. In order to obtain optimal images, a layer of gel will be applied to the area being imaged so that good contact is made between your skin and the ultrasound probe. The probe will be placed directly onto the gel and your skin for the duration of the examination. You may also be asked to hold your breath for a few seconds during the scan time. The scan is completely painless, although pressure may be applied to improve the image quality. Please tell the sonographer should this become uncomfortable.
In some instances a transvaginal scan may be indicated. Transvaginal scans are frequently performed in the first trimester of pregnancy and also in the late stages of pregnancy and at other times to get a close up view of the pelvic organs. The transvaginal scan is performed with an empty bladder, and as a result many patients find it more comfortable. The small sterilised probe, about the same diameter as a thumb, is lubricated with gel before being inserted into the vagina. A protective cover (a condom) is placed over the transducer each time it is used, so there is no risk of infection. Transvaginal scans are only performed if requested by your referring doctor or clinically indicated and always with the patient’s consent. Please discuss any issues you may have with the sonographer.
Indications for Pregnancy Ultrasound
Ultrasound is a highly valuable diagnostic tool and it is particularly useful during pregnancy because it is completely safe for you and your baby. Some of the useful indications for use during pregnancy are:
- for dating purposes and to accurately determine your due date
- to ascertain the number of babies present
- to check for any bleeding early in the pregnancy
- to check the position of the placenta
- to assess the growth of the baby and its general well-being
- to provide information about the anatomy of the baby and check for possible abnormalities*
*not all possible birth abnormalities are reliably diagnosed using ultrasound and all scan results should be interpreted within the limitations of the test.
How long will the Procedure Take?
Most ultrasound examinations will be completed within half and hour, however, some studies will take longer especially if a transvaginal scan is indicated after an abdominal scan is performed. It is not unusual for the radiologist to come in and speak with you and view the images on the screen. The radiologist will then interpret all images produced during the examination and the results will be forwarded to your doctor. We can provide you with some still pictures or a CD from your scan should you wish. We do not provide video tapes of your ultrasound examination.
Please remember to bring any previous ultrasound or x-ray films to your appointment.