Pregnancy Ultrasound Scans

Pregnancy Ultrasound

This is an 'echo picture' formed using very high frequency sound waves.   The ultrasound machine sends out millionsof tiny sound waves (at a frequency much higher than we can hear) and then 'listens' for the returning echoes from the baby and its surroundings. A powerful computer converts this information into a black and white image.

Is it safe?

Absolutely. No ill-effects have been reported in 30 years of scanning and millions of scans.

Is there any preparation?

If you are less than 14 weeks pregnant you will need to have a full bladder. After 14 weeks, please refrain from going to the toilet for one hour prior to your scan.

What will happen to me?

You will lie down on the scan couch; some warm gel is placed on your abdomen. The sonographer places the sound probe on the gel to make the image.

Occasionally when we need more detailed information we can do an internal scan. This is often helpful when we are trying to confirm an early pregnancy.

The scan times range from five minutes to half an hour, depending on the reason for the scan.

 Nuchal Translucency Scan

 An early pregnancy scan

The nuchal translucency (NT) scan is performed when you are between 11 and 14 weeks pregnant.  During the scan we confirm how many weeks pregnant you are and look for any major problems with the development of the baby.

Most babies are born healthy, but women of any age have a risk of having a baby with a physical or mental abnormality.  In some cases the abnormality is due to a problem with the baby's chromosomes (genetic instructions).  The risk of  a baby having a chromosomal abnormality increases with the age of the mother.

The most common chromosomal abnormality is having and extra chromosome (Down syndrome) and the NT scan  combined with Maternal Serum Blood test results gives an estimate of the risk of the baby having this abnormality.  We emphasise that this is an estimate only, and the only way to be certain that your baby does not have a chromosomal abnormality is to have a test called amniocentesis, which you can discuss with you doctor or midwife.

Having your scan

Your examination will be carried out by a sonographer (a technologist who is trained in using ultrasound equipment) or a radiologist ( a doctor who specialises in ultrasound and x-ray examinations).  The examination is painless and will not harm you or your baby.

A measurement of the nuchal translucency (the fluid at the back of the baby's neck) is performed using ultrasound.  Most babies have a small amount of the fluid and an increased amount of fluid can mean an increased risk of a chromosomal abnormality.

The nuchal translucency scan is performed at 11 - 14 in the pregnancy and your doctor or midwife will tell you when to telephone Nelson Radiology for an appointment.

The combination of both the scan and Maternal Serum Blood test gives you an estimate of the risk of your baby having a chromosomal abnormality, but if you wish to have a definite answer about your risk, discuss amniocentesis with your doctor or midwife.

In all pregnancies, it is important to have another scan at 19 - 20 weeks to look for any problems that are not due to chromosomal abnormalities.

If you have any questions about your scan, please discuss these with your doctor or midwife.


Finish drinking 1 large glass of water one hour before your scan.  Don't empty your bladder again until after the scan.


There will be a surcharge for your scan unless you have a Community Services Card - please bring this with you.