Nuchal Translucency Scan
Nuchal Translucency screening was introduced in 1996 as a screening test, designed to identify the fetus that was at high risk for aneuploidy (extra chromosomes including Downs syndrome), regardless of a mother’s age. As data has been collected internationally, it has been found that patients who have a low risk for aneuploidy, have a better than expected pregnancy outcome.
Conversely, patients who are at high risk for aneuploidy, but with a fetus with normal chromosomes are more likely to have pregnancy complications.
If the fetus has a thick fluid collection in the neck, that fetus has an increased risk for a cardiac anomaly or a diaphragmatic hernia. If the risk has been increased due to adverse blood results, the risk is then increased for pre eclampsia (high blood pressure), APH (hemorrhage), pre-term delivery and IUGR (intrauterine fetal growth restriction).
Thus, first trimester screening, using ultrasound, beta HCG and PAPP-A, PlGF & AFP is the best assessment tool we have to sort pregnancies out into the risk groups – either a HIGH risk or LOW risk for an adverse outcome.
We are now also able to screen for pregnancy complications at the time of the Nuchal Translucency scan.
The baby having low birth weight
The chance of the mother having a premature delivery
The chance of the mother developing pre-eclampsia
The Fetal Medicine Foundation has developed this screening using:
Mother's blood pressure
Mother's medical history
The resistance in the uterine arteries of the mother
Additional biochemistry (blood tests) that is taken at 10 - 11 weeks gestation, when the Nuchal Translucency blood test is done.
At the end of the scan, provided we have all this information, we can assess whether the patient is high or low risk for developing these complications. We can also assess if the patient is high or low risk of having a fetus with Trisomy 21 (Down syndrome), Trisomy 13 and Trisomy 18.
At this stage we are the only practice in Queensland offering the screening for these pregnancy complications.
The Nuchal Translucency scan (NT) is an ultrasound performed between 11 weeks 3 days and 13 weeks 6 days in conjunction with a blood test. However, we try to organise your appointment for between 12 weeks and 13 weeks 2 days. This means that should your baby measure a little small for dates, you do not have to come back to have the scan repeated. Alternatively, if your baby is big for dates, we can still undertake the assessment.
It is important to note that the NT scan is a screening test, not a diagnostic test. The nuchal translucency is a fluid collection located at the back of the fetus’ neck. All fetuses have this fluid collection and it is well visualised towards the end of the first trimester. We know that a fetus with Down syndrome will usually have a much larger fluid collection than a fetus that does not have Down syndrome.
When a woman is pregnant, there are four hormones she produces that may vary if a baby has Down syndrome. The levels of these hormones are measured ideally between 10 and 11 weeks gestation, prior to the ultrasound being performed (whenever possible). If they are found to be in the normal range, this decreases the chance of the baby having Down syndrome. Once the nuchal translucency is measured and the scan is complete, the sonographer will enter the information from the scan and the blood test into a computer programme which will assess the risk for this particular fetus.
The results would be given to you as either 'high risk' or 'low risk' of the fetus having a chromosome anomaly. For us, the patient 1:100 or worse would be considered high risk. A patient 1:101 to 1:1000 would be considered moderate risk and a patient with a risk better than 1:1000 would be considered low risk.
If you have missed the opportunity or choose not to have a Nuchal Translucency Screening scan a first trimester scan can still provide an opportunity to check the baby for many fundamental abnormalities such as limb defects or major heart defects etc.
All scans in our Practice are performed by sonographers fully accredited with the Fetal Medicine Foundation (London). Once fully accredited, the Australian and New Zealand College of Obstetricians and Gynaecologists requires that all sonographers and practices are strictly audited annually to ensure their high standard is maintained.