Every foetus has a layer of fluid along the back of their neck. The thickness of this fluid can be measured during an ultrasound scan at this early stage of pregnancy. This measurement can be used to determine whether the baby is at increased risk of major chromosomal abnormalities such as Down Syndrome.
Chromosomes contain the DNA that make up each person’s genetic blueprint. Sometimes the number or the arrangement of these chromosomes are abnormal, and can result in various syndromes. The most common of these chromosomal abnormalities is Down Syndrome. A chromosome problem is possible in ANY pregnancy. Although the risk increases with age, the vast majority still occur under the age of 35, as this age group have 90% of all babies.
Preparing for a Nuchal Translucency scan
Please bring your referral (letter from your doctor) and your Medicare and/or Pension Health care card with you to your appointment. It is important to bring all previous films and reports relating to the region being imaged. It is important that you are on time for your appointment to ensure there is sufficient time available to perform the procedure.
To ensure clear images, you will be asked to attend with a full bladder. This is achieved by emptying your bladder 2 hours before your appointment and then immediately drinking 600ml of water. Do not empty your bladder again before the procedure. You may eat normally and take any necessary medication.
The ultrasound waves are transmitted and collected via a hand held probe which is moved over the abdomen. You will not feel any pain or discomfort.
Your procedure will take approximately 30 minutes.
We use the Nuchal Translucency measurement obtained from the ultrasound scan, and combine it with other information such as the mother’s age and the results of a simple blood test, to calculate a risk estimate. The detection rate for Down Syndrome is 85-90% when all this information is combined.
The blood test measures two chemicals, called free beta-hCG and PAPP-A, that are produced by the placenta that cross over into the mother’s bloodstream. If there are chromosomal abnormalities, the levels of these chemicals can give us an indication of a potential problem.
The results of your Nuchal Translucency scan will usually be ready in 48 hours. Norwest Medical Imaging strongly advises that you return to your referring doctor, in order for your doctor to discuss your Nuchal Translucency report with you. They can also be provided on CD or electronic transfer to your referring practitioner if requested.
Should I have this Prenatal testing?
This is a personal and individual decision. The pregnant woman and her partner should have counselling with her doctor before undergoing the test, to gain a good understanding of the screening test, and to determine the implications of the test results. A screening test assesses risk – it does not definitively confirm or exclude the presence of an abnormality.
What does a low risk result mean?
A calculated risk of less than 1 in 300 (for example 1 in 1000) suggests a low risk. As this is a screening test, it is important to understand that a LOW risk is not the same as NO risk.
What does a high risk result mean?
A calculated risk greater than 1 in 300 (for example 1 in 100) is considered an increased risk, but once again this does not mean the baby will definitely have a chromosomal abnormality. The woman will need to discuss with her doctor whether to proceed on to have further prenatal investigations (such as amniocentesis or chorionic villus sampling).
What are the benefits of a Nuchal Translucency scan?
- Non-invasive screening test for chromosomal abnormality with a high detection rate
- Accurate dating of the pregnancy
- Diagnosis of twin or multiple pregnancies
- Diagnosis of early pregnancy failure
- Assessment of early structural development of the baby
A further ultrasound at 18 to 20 weeks is recommended as this is the best time to detect the majority of structural defects in the baby. The foetus at this stage is quite developed and in most cases the head, face, limbs and movements can be observed during the scan.
Can I eat before having a Nuchal Translucency ultrasound?
You can eat before your ultrasound. You are required to have a full bladder. It is necessary to drink 600-800ml of water two hours prior to the scan and refrain from going to the toilet before the scan.
Can I have a female sonographer/technician to perform the scan?
Yes, please let reception know when making your appointment. We have female radiographers and sonographers sensitive to the needs of female patients.
Is this test safe for my baby?
Ultrasound is a very safe and accurate investigative tool used to assess many organs in the body. Ultrasound uses harmless high frequency inaudible sound waves to obtain images. Ultrasound waves are not dangerous or irritating to adults or children. There is NO radiation with an ultrasound examination.
Will the sonographer performing my scan tell me what’s wrong?
It is the sonographer’s duty to perform the test and ensure the images are of high quality for the radiologist (specialist doctor) to interpret them.