Antenatal Care Nuchal Translucency Nt Scan

Nuchal (pronounced ‘new-cal’) translucency is a scan carried out during pregnancy whose purpose is to screen a baby for Down’s syndrome. NT is currently the most accurate technique used for estimating chances of Down’s syndrome. It is non-invasive and painless, and carried out using ultrasound when the baby is aged between 11-13 weeks + 6 days old. All babies have Nuchal translucency, but babies with Down’s syndrome have high NT. The scan also checks other rarer conditions like Edward’s and Patau’s syndromes.

How Nuchal translucency (NT) scan is performed

Nuchal translucency (NT) is performed through the mother’s tummy. However, in special cases, it will be carried out through the vagina to give clear results. The doctor will measure the baby from head to bottom of its spine, and width of the Nuchal translucency. Normally, during the scan, the fluid appears black and the skin white line.

Also, the mother gets to see her baby’s major parts like the head, and limbs. The scan will also help identify other abnormalities although it is recommended to get another scan during the 20th week for detailed results.

What is a normal Nuchal translucency measurement?

A measurement of about 2mm and 2.8mm at 11 weeks and 13 weeks +6 days respectively is considered normal. A baby with a low measurement (small NT) has low risk of Down’s syndrome although the NT grows in proportion with the baby. Fortunately, some babies with increased NT do not have chances of developing Down’s syndrome. Increased NT not only suggests Down’s syndrome but also at risk of other chromosomal abnormalities.

How Nuchal translucency (NT) results are calculated

It is believed that every woman has chances of delivering a baby with Down’s syndrome, but chances increases as she ages. To calculate the results, the mother’s age, blood tests, baby’s heart rate, and NT scan measurements are entered into a database. The database contains results containing risk records for other mothers at this age. The NT results are then calculated to generate the risk. General risks however, can be greater or less than risk for most women of this age although they will depend on the NT measurement.

Advantages of Nuchal translucency (NT)

The main advantage of Nuchal translucency (NT) scan is ruling out risks of Down’s syndrome and other rarer conditions like Edward’s and Patau’s syndromes. Also, the scan will help the mother decide her way forward with the pregnancy. If the results suggest the baby is already infected, it will give the mother the chance to choose whether to carry on or terminate the pregnancy. This will also prevent late abortion that involves induced labor.

Sources: Nuchal Translucency Scan

BabyCenter- Nuchal translucency (NT) scan

Genetic of Pregnancy Encyclopedia- An Infant with Down’s Syndrome