Frequently Asked Questions
What is an NT Scan?
A Nuchal Transparency (NT) Test is scheduled between 11 to 13 weeks of the pregnancy to screen the fetal abnormalities if any. It is a sonographic test that screens chromosomal abnormalities and even extracellular matrix and lymphatic drainage can also be screened in this test.
What is the purpose of the NT Scan?
A common screening test is done in 1st trimester of pregnancy is an NT Scan. This test screens the size of Nuchal Translucency that is present clearly at the back of the baby’s neck. Little clear space at the back of the neck of the fetus is not common, but too much clear space indicates Down Syndrome or other chromosomal abnormalities such as Edwards Syndrome or Patau Syndrome. The cells in the body contain a nucleus that has all the genetic material inherited from the parents. Generally, there are 23 pairs of chromosomes in a nucleus that are inherited equally from each parent. In the case of Down Syndrome, there is an extra copy of chromosome 21.
Down Syndrome can’t be cured and causes delays in the development of the fetus and other distinct physical features include:
- Small stature
- Upward slanted eyes
- Low muscle tone
Down syndrome is the most common genetic condition and Edwards Syndrom & Patau Syndrome are rare but fatal genetic abnormalities and the babies born with it dies within a year after birth.
When should be NT Scan scheduled?
The NT Scan should be done in 1st trimester as the clear space behind the baby’s neck can disappear in week 15. This test also screens blood work that helps measure the plasma protein and HCG (Human Chorionic Gonadotropin). Abnormal levels of any of these indicate abnormal chromosomal abnormalities.
How does an NT Scan Works?
- The screening is done by the doctor or the technician taking the abdominal ultrasound.
- The alternative method such as a transvaginal test can also be done where the probe is inserted through the vagina for the clear picture.
- The ultrasound used is of high-frequency sound waves that create the image of the fetus from inside the mother’s body.
- After the image is obtained, the doctor or the technician measures the translucency and or the clear space behind the fetus’s neck.
- Then the age of the mother is added to the system to calculate the risk of the baby having any abnormalities.
- The main thing taken into consideration is that the NT Scan cannot diagnose any chromosomal abnormality but can only predict the same.
- The accuracy rate varies as the test only predicts hence by combining NT Scan with blood testing the accuracy of the screening is 85% for predicting the risk of Down Syndrome.
- If the blood test is not done along with the NT Scan, then the accuracy rate drops to 75%.
How to prepare for an NT Scan?
- NT Scans are carried out by trained and professional Sonographers. The scans are carried out in dimly lit rooms so that the sonographers can see the scans properly on the screen.
- The patient is asked to full the bladder as the scan are more clear when the bladder is full.
- The patient will be asked to lie down on the bed or couch and asked to lower the bottom she is wearing till the hips and lift the top till the chest hence the abdomen is bare.
- The gel is applied to the abdomen to make good contact between the abdomen and the probe used during sonography and a black and white image of the fetus is seen on the screen.
- Usually, the scans don’t hurt but the sonographer has to apply little pressure on the abdomen to get the better visuals of the fetus.
- The scan usually takes around 30 minutes.
Is NT Scan a screening test or diagnostic scan?
Any inconclusive or positive test can be frightening for the new parents to be. Hence it is necessary to know that an NT Scan can only predict the risk. This test isn’t offering a definitive answer about the genetic abnormalities as it is only a screening test, not a diagnostic test. The purpose of the NT Scan is to know the risk factors of a particular condition. Whereas, a diagnostic test is done to confirm the condition or abnormality in the fetus.
What is the upshot of an NT Scan?
- NT Scan is a noninvasive and safe test that doesn’t cause any harm to the mother or the baby.
- This test has to be done in 1st trimester but to undergo this test is optional.
- Some mothers-to-be skip this test as they don’t want to know the risks.
- Anyway, the mother-to-be can always talk to her doctor in case of anxiety and or are worried about the results.