NT Scan; What to expect and why it is done

NT scan

What is the Nuchal Translucency or NT scan?

At 11 weeks, your next scan is the all important Nuchal Translucency (NT) scan. This is also called the “first trimester scan”. This scan uses ultrasound primarily to ascertain whether your baby is at the risk of having Down syndrome or some other chromosomal abnormalities. It also is a test to check for major congenital heart problems in the foetus.

Here is where your doctor will be able to check for the first marker - babies with increased fluid at the base of their necks (nuchal fold) have the possibility of having an extra chromosome - resulting in a chromosomal disorder. The ultrasound allows the measurement of this fluid as the base of the neck is still transparent. The timing is especially crucial because the base of the neck starts to get opaque as your baby grows. The NT scan is used to screen for congenital heart defects, chromosomal defects, Down’s syndrome and other genetic disorder.

Are the results of an NT scan definitive?

The test results are usually given in terms of percentage probabilities. It is read as the probability of your child having a NT defect. In case the doctor suspects that your baby is at an increased risk of having a NT defect, further tests are offered to reconfirm.

The results of this scan can be read in combination with a second trimester blood test as well. This combined blood test result will provide a risk assessment using 4 completely different markers found in the mom’s blood stream.

Please understand that the nuchal translucency test don't actually have a direct relation to a chromosomal test neither do they diagnose a specific condition. The results give the statistical likelihood of the possibility of a problem. Getting an abnormal result in the NT test and/or blood test doesn’t necessarily mean that your baby will definitely have a chromosomal defect. It only means that the baby is at a high risk of it. A lot of women who get an abnormal result on their screening end up having a perfectly normal and healthy child. All the same, at the other end of the spectrum, some with a normal result may end up with a baby who has a chromosomal defect, although it is extremely unlikely.

The NT scan can however detect approximately 80 % of Down syndrome and 80 % of trisomy 18 problems successfully.

Risks associated with the NT scan

The NT scan is noninvasive and is completely painless. They might evoke anxiety though, because it is undertaken to determine serious medical and developmental abnormalities in the foetus. Both false negatives and positives are entirely possible. In these cases, follow-up tests will be conducted. But think of it in a positive spin - the likelihood of having a normal baby is entirely in your favour.