Nuchal translucency (also spelled Nucal translucency) is a non-invasive prenatal test done during the first trimester (between 11 ½ and 14 weeks) via ultrasound to determine the risk of Down Syndrome. The high resolution ultrasound that is performed looks at the nuchal area (a fold that is located in the back of the neck). If the nuchal translucency or “NT” reading is greater than 3mm it is referred to as “increased NT”. This would not necessarily mean that the baby has Down syndrome or a chromosome disorder, but that the baby is at greater risk for these types of disorders.
This test has been performed in the United States since about 1995, but it is still not widely available. Technicians that perform this test must be specially trained and use high quality equipment, making the test difficult to find in some areas. As more time passes, this test is becoming more widely used, so you should check with your doctor or midwife to see if it is available during your pregnancy. Because this is a non-invasive test, it poses no risk to you or your baby and it is painless. This makes it a great option to see if further invasive testing is needed or desired.
If an increased NT risk is determined the parent then would have the choice of undergoing CVS or amniocentesis for a diagnosis. The detection rate is 80% for nuchal translucency by itself. If the baby has an increased risk you may choose to continue your pregnancy without further testing. The advantage to the testing is that you would have a definite answer, but the downside is that the invasive testing does carry a small (1%) risk of miscarriage. You should fully discuss the options with your doctor or midwife.