What is a (Nuchal Translucency Scan) NT scan ?

A (Nuchal Translucency scan) NT scan is an ultrasound scan performed to rule out any structured malformations caused by chromosomal abnormalities of the baby. Nuchal Translucency is the fluid-filled space behind the baby’s neck. NT scan checks this fluid space and the nasal bone of the baby. The nasal bone is a bright echogenic space found between the tip of the baby’s nose.

In addition to this, the blood flow and various other body parts visualized in the first trimester are also examined.

Nuchal translucency Scan Test (NT Scan) in Chennai

Chennai Women’s Clinic at T. Nagar  is the top choice for NT Scan in Chennai by many moms-to-be. Getting your NT scan at Chennai Women’s Clinic means you can entrust your baby’s welfare in the hands of an award-winning Obstetrician and Gynecologist in the city, Dr Deepthi Jammi. Watch this video above, where she explains the detailed procedure of the NT scan scan.

When is the NT scan taken?

An NT scan is taken between 12 to 13 weeks of your gestation. The last day you can undergo an NT scan is when you complete 13 weeks and 6days of your gestation. This is the maximum time frame recommended since your baby’s neck will be transparent until then, which helps measure the fluid behind the baby’s neck.

Why should you take an NT scan?

Fetal Medicine specialists check the nuchal Translucency (A collection of fluid under your baby’s skin at the back of the neck) and nasal bone of the fetus to assess the risk of Down’s syndrome. The measurement of this fluid is termed nuchal translucency measurement.

All the unborn babies will have some amount of fluid in this space. However, pregnancies with chromosomal abnormalities or other health concerns show increased fluid. Besides, there can be an absence of the nasal bone with this.

NT Scan

This nuchal measurement, along with the patient’s age and date of the pregnancy, is used to calculate the risk for Down’s syndrome, trisomy 13 and trisomy 18.

How to identify Down's Syndrome

Generally, a baby inherits 46 chromosomes from the parents (23 from the mother and 23 from the father). Whereas, for a baby with Down’s Syndrome, there are three copies of chromosome number 21. Such people have 47 chromosomes instead of the usual 46 (23 pairs). The extra chromosome appears with the 21st pair.

Down Syndrome Chromosomes

40% of Down’s Syndrome cases do not exhibit structural abnormalities in a scan. Trisomy 18 and Trisomy 13 ( carrying the same risk factors) are less common than Down’s syndrome. These are other genetic disorders carrying serious conditions, including birth defects, severe disability, and shortened life span. Most of these are diagnosable during the prenatal window.

What happens if a baby is in the high-risk category

  • You are offered genetic counseling by your fetal expert if,
  • Your NT scan detects the presence of abnormalities in the baby along with any soft markers. Soft markers are fetal sonographic findings that indicate an underlying chromosomal or non-chromosomal abnormality.

During the genetic counseling, your fetal expert recommends two different types of confirmatory testing,

  1. An invasive diagnostic procedure called Chorionic villus sampling (CVS):

    During this procedure, you will be guided by a scan to pass a needle through your abdomen to collect chorionic villi (placental tissue) samples for testing. This is a 100% confirmatory test for any chromosomal disorders in your baby. 

  1. Non-invasive Prenatal Screening (NIPT):

    The procedure involves collecting 20ml of your blood from the arms to test for its fetal cells. In general, this analysis is not done in India. Rather the sample is sent abroad for analysis. This is a high-quality screening test and carries no chances of miscarriage. In contrast, the CVS procedure is usually a confirmatory test and carries a small risk percentage of miscarriage. 

Down syndrome Test

What can be done if you miss the first trimester NT scan

A second-trimester (16 to 20weeks) screening test is offered if you have missed the first trimester NT scan. However, the test sensitivity for Down’s Syndrome in this is lower than the first trimester NT scan. 

This is quadruple testing to assess the four blood markers in your blood,

  1. Alpha-fetoprotein (AFP)
  2. Human chorionic gonadotropin (hCG) 
  3. Estriol (uE3)
  4. Inhibin A

Note: An early anomaly scan is performed before this test. And if your anomaly scan doesn’t show any significant abnormalities, you are not recommended with quadruple testing. However, you will be recommended with an Amniocentesis in case of any abnormalities. This is an invasive procedure where a needle is passed through your abdomen to collect the amniotic fluid surrounding the baby for testing. 

Does a low-risk first-trimester blood test guarantee a healthy baby?

The answer is NO.

A blood test with a low risk does not guarantee that your baby is not affected by Down’s syndrome. Likewise, a report with high risk doesn’t guarantee that the baby will be born with Down’s Syndrome. 

This is only a screening test, and if required, a confirmatory test has to be performed after a detailed consultation with a Fetal Medicine expert

An anomaly scan at 20 weeks is recommended if you have a low-risk test to rule out the risk possibilities.