What Does a Nuchal Translucency Ultrasound Test For?
Ultrasound tests use high-frequency sound waves to create an internal image of the body. With nuchal translucency ultrasound tests, the scan is carried out on pregnant individuals as part of the first-trimester screening tests, and we use an extremely advanced ultrasound system for more precise results. A nuchal translucency ultrasound tests for the statistical likelihood of chromosomal disorders. This test is a helpful tool used to reassure expectant parents that the baby is in good health.
What is Nuchal Translucency?
In the base of the neck of the fetus is the nuchal fold, which is where nuchal translucency fluid is stored. If this fluid is thicker than in typical measurements, this could indicate a higher risk of Down’s syndrome (trisomy 21), Patau’s syndrome (trisomy 13), or Edward’s syndrome (trisomy 18).
How is a Nuchal Translucency Test Conducted?
A nuchal translucency ultrasound test is a non-invasive scan.
The ultrasound wand–which is connected to the ultrasound machine–is dragged along the tummy of the mother-to-be to create an image of the baby. Sometimes, depending on the position of the womb and the baby, the transvaginal method is used to get a better view of the fetus. This test poses no risk to the baby and should not be uncomfortable.
During the test, the sonographer will measure the length of the baby from crown to rump (CRL) to assess the gestational age of the fetus. Next, the sonographer will measure the thickness of the fluid in the nuchal fold (at the back of the neck). With these measurements, along with the age of the mother and the maternal hCG and PAPP-A levels, the sonographer will calculate the probability of any chromosomal disorders.
The nuchal fluid becomes thicker as the pregnancy advances, which is why the scan should be conducted between 11+1 and 13+6 weeks of the pregnancy for the best results.
What Does a Nuchal Translucency Ultrasound Test Determine?
As mentioned above, the test will gather information pertaining to potential chromosomal disorders. These are disorders such as Down’s syndrome (Trisomy 21), Edward’s syndrome (Trisomy 18) and Patau syndrome (Trisomy 13). In these instances, the fetus has an extra chromosome, be it chromosome number 21, 18 or 13.
As this is a screening test, alone this test does not offer definitive results but rather a statistical likelihood of such disorders. For example, you will be told that your baby is low or high risk for Down’s syndrome. When paired with typical first-trimester screening, the results are 83% to 92% accurate. If the sonographer notices that the nuchal translucency fluid is thicker than in most cases, they may suggest the mother undergo further testing for definitive results.
What Other Tests Can be Conducted?
The nuchal translucency ultrasound is popular because it is non-invasive, but in the event your baby is high risk for Down’s syndrome, further tests are required. The sonographer may suggest either a chorionic villus sampling (also known as a CVS) or an amniocentesis ornon-invasive prenatal testing (NIPT). CVS and amniocentesis carry a slight risk – 0.5% to 1.0% – of miscarriage because of their invasive nature. Before making the decision to proceed with one of these invasive tests, it may be worthwhile considering an NIPT. NIPT is a blood test which can look for free-fetal DNA in your maternal blood stream. The lab can further determine whether your baby is at risk for Down’s syndrome and this information can be invaluable when making a decision to proceed or not with invasive testing.
At OMNI, our sonographers are accredited by the Fetal Medicine Foundation to conduct nuchal translucency ultrasounds. For advice, information or to book your ultrasound, get in touch with us today.