What is ultrasound?
Ultrasound is high frequency sound which is outside the range of human hearing. The examination is sometimes called a scan or a sonar. Sound waves are created by a small metal crystal within the ultrasound transducer. Soundwaves pass into the body and are reflected off internal organs. The ultrasound machine is able to analyse the returning echoes and convert them into pictures which are displayed on a television screen. Pictures of both normal and abnormal internal organs are displayed on the screen.
Is ultrasound Safe?
Diagnostic Ultrasound has been used commonly on large populations from the 1960s. Safety has been the subject of ongoing scrutiny. The Australian Society for Ultrasound in Medicine Statement (ASUM) concludes: There is no convincing evidence that diagnostic ultrasound causes adverse health effects in human patients. ASUM however acknowledges that epidemiology data has several limitations. Ongoing research may reveal factors now not known. More research is always needed.
Good practice, therefore, limits ultrasound exposure to situations where benefit is anticipated. The ASUM safety recommendation is that care be taken to “ensure that examinations are performed prudently using the ALARA (as low as reasonably achievable) principle of applying lowest acoustic output and dwell time consistent with that required to obtain the necessary diagnostic information”.
How is an ultrasound examination performed?
Ultrasound waves are sent out from a transducer which is usually moved over the skin of the abdomen. Warmed gel is applied to the skin before the scan to allow the ultrasound waves to pass from the transducer into the body. There is no pain associated with the examination. The ultrasound examination may also be performed by placing a small transducer into the vagina. This transducer is smaller than a vaginal speculum and usually causes minimal discomfort. This is used in the early weeks of pregnancy and to exam the uterus and ovaries in non-pregnant women. Between patients the transducer is cleaned and disinfected to prevent cross infection. A new protective cover is used for each examination. If you have any concern regarding vaginal imaging please discuss this with your referring doctor. Family members and friends are welcome to come with you for your pregnancy ultrasounds. Children are welcome but if possible another adult should be present to look after them should they become restless.
Will I be able to know the sex of my baby?
The 20 week ultrasound is very accurate in determining the sex of the baby. It is correct 99% of the time. At the 11 – 14 week ultrasound it is sometimes possible to sex the baby but not as accurately. In 10% of cases it is not possible to sex the baby and where sexing is done it is wrong 10% of the time.