The Nuchal Translucency Screening is a test that can help determine your baby’s risk of having certain birth defects, most notably Down’s Syndrome. In addition, the test can show certain heart defects and other chromosomal abnormalities. This test is most often done on mothers who are considered at increased risk due to advanced maternal age.
If you are offered this test, it’s important to understand that this is a screening test. It does not give a definitive diagnosis, but shows that a baby may be at increased risk of having certain abnormalities. A combination of ultrasound and a blood test are used to determine this risk.
If the test shows that your baby is at an increased risk for Down’s Syndrome, this doesn’t mean the baby definitely has it. Further testing would be needed to offer a definitive diagnosis. An amniocentesis or chorionic villus sampling can be done to give a true diagnosis. A level 2 ultrasound can also be done, if you are uncomfortable with the risk of the amnio.
The test is generally done between the eleventh and fourteenth week of pregnancy. The test involves an ultrasound of the back of the baby’s neck. This area has a clear space, which is known as the nuchal fold. In babies with Down’s Syndrome, this clear space tends to be larger than in healthy babies.
This is not a typical ultrasound. A special, high resolution machine is needed to perform this test. The ultrasound tech or doctor must have specific training in using the machine and conducting the test. For this reason, the test isn’t offered by all doctors. You may be referred to a larger hospital to have the test.
The measurements of the nuchal fold, the age of the mother and the number of weeks gestation are used to calculate the baby’s risk. In addition, the results of the blood test are used in the calculation of risk.
The main benefit of the test is knowing if there is an increased risk of your baby having a chromosomal defect. What you do with that information will be up to you and your doctor. The degree of risk may factor into your decision about having further testing. If your risk is slightly elevated, but still fairly low, you may decide to forego further testing. If the risk is higher, you may want to have further testing for a more definitive diagnosis.