A Nuchal Translucency (NT) scan is an optional first-trimester prenatal screening of pregnancy, typically between 11 and 14 weeks.
This ultrasound measures the thickness of the fluid behind the baby’s neck, helping to assess the risks of chromosomal abnormalities such as
- Patau syndrome
- Down syndrome
- Edwards syndrome
The NT scan is a screening tool and does not diagnose any condition but can indicate if further testing is needed.
Purpose of the Nuchal Translucency Scan
The primary purpose of the NT scan is to evaluate the likelihood of chromosomal or genetic conditions in the foetus.
An increased measurement of the fluid behind the neck can indicate a higher risk of conditions like
- Down syndrome (trisomy 21)
- Edwards syndrome (trisomy 18)
- Patau syndrome (trisomy 13).
The NT scan can also help identify potential congenital heart defects, among the most common congenital disabilities.
Detecting these issues early allows for timely medical intervention and informed counselling for the parents.
Procedure for the Nuchal Translucency Scan
The NT scan is performed using abdominal ultrasound or, in some cases, a vaginal ultrasound.
During the procedure, a transducer is moved over the mother’s abdomen after applying ultrasound gel, producing images of the baby on a screen.
The fluid-filled space behind the baby’s neck is measured in millimetres.
When combined with first-trimester blood test results, this measurement provides a comprehensive risk assessment.
The ideal time for the NT scan is when the foetus measures between 45 and 84 millimetres from crown to rump, as the fluid is reabsorbed by the body after 14 weeks, making it challenging to measure later.
Interpreting Nuchal Translucency Results
The results of the NT scan are typically combined with maternal blood test results to calculate the overall risk of congenital conditions.
An average amount of fluid suggests a lower risk, while an increased fluid measurement indicates a higher risk.
For instance, a result might show a 1 in 300 chance, meaning that out of 300 babies with a similar
NT measurement, only one might have a congenital condition. However, an abnormal NT result does not confirm a diagnosis; it suggests further testing, such as
- Chorionic villus sampling (CVS)
- Amniocentesis
to confirm the presence of a genetic condition.
Follow-Up and Next Steps
An abnormal NT result might also lead to a fetal echocardiogram to examine the baby’s heart more closely.
It’s important not to panic if you receive an irregular result, as it does not necessarily mean your baby has a problem.
Further tests or consultations with a genetic counsellor can provide more clarity and help you understand the risks and implications of the results.
Most doctors can interpret the NT scan on the same day, but blood test results may take a few days or weeks to process, after which a more comprehensive risk assessment will be provided.
Curious about your baby’s development? Schedule your NT scan now to learn more about their health and growth!
