The NT scan, also called the neck translucency scan, is a non-invasive ultrasound performed on pregnant women between the ages of 11-13.6 gestational weeks to detect the risk of chromosomal abnormality.
How is the test performed?
The test is performed when the fetus is between 11 weeks and 13 weeks and 6 days of age. The test is performed with a high-end ultrasound scanner that uses sound waves to form images of the fetus. The scan is performed by a radiologist or, sometimes, a gynecologist or a trained sonologist. The image must be taken with great precision and multiple criteria are taken to ensure that the image is optimal. The skin on the back of the neck forms a bright band on the scan image and this is measured. Other structures such as the nasal bone are searched simultaneously.
What is the use of the test?
The test is performed to ensure that the baby born is free of chromosomal defects such as Down syndrome, Turner syndrome, trisomy of chromosome 18 and 13 and triploidy. While no test can offer a 100% guarantee, this test along with some blood tests (triple marker test) can provide a reasonable detection rate for these problems.
Who is the exploration for?
There are certain high risk populations where there is a higher probability of chromosomal abnormalities. These include the average maternal age of 35 years and the previous fetus with anomalies. However, in practice, even young mothers can undergo these tests, as they even have a small risk (1 in 1400) of having children with chromosomal abnormalities, and the benefit of knowing much more than the cost of the test.
How accurate is it?
The nape scan alone detects 62% of all Down syndrome with a false positive rate of 5.0%; The combination with the blood test gives corresponding values of 73% and 4.7%.
When the screening test is positive, chorionic villus sampling (CVS) or amniocentesis tests are required to confirm the presence of a genetic abnormality. However, this procedure carries a small risk of miscarriage, so a prior examination with low false-positive rates is necessary to minimize the possibility of miscarriage.
Read the full article "What is an NT scan?" Written by Dr.Sudhir Pudi at Practo.com here: https://www.practo.com/healthfeed/what-is-an-nt-scan-9746/post
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