What is a Nuchal Translucency Scan (NT scan)?

A Nuchal Translucency (NT) scan is an ultrasound scan taken between 12 to 13 weeks of your gestation. This scan is performed to rule out any structured malformations caused by chromosomal abnormalities in the fetus.

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.

Best NT Scan in Chennai

Chennai Women’s Clinic at T.Nagar (Homepage internal link) is the top choice for NT Scan in Chennai by many moms-to-be. We at Chennai Women’s Clinic offer you the best obstetric scan services in Chennai, providing you and your unborn with a clean and positive environment.

Here, your scans are done by the award-winning Obstetrician and Gynecologist in the city, Dr. Deepthi Jammi (Founder & Fetal Medical Consultant, Chennai Women’s Clinic). Our doctor and her team give their best to ensure premium-level health for you and your child.

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.

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.

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.

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.

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

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

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.
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.

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.

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.
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.

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.

Frequently Asked Questions

01. What is the normal range of the NT scan?

An NT scan measurement upto 2.8mm around 13weeks is considered as normal

02. What is the difference between NT scan and anomaly scan?

NT scan is an ultrasound scan that mainly helps to assess your developing baby’s risk of having Down syndrome and some other chromosomal abnormalities. While an anomaly scan is used to look for any abnormalities in your baby’s body parts.

03. How long does NT scan take?

An NT scan takes about 20 minutes to 30 minutes for completion.

04. Is NT Scan painful?

NT scans are not painful. They sometimes might cause discomfort as you may feel some pressure when the sonographer presses on your abdomen to get a clear picture.