Nuchal Translucency (NT) is a test that is used as a screening tool for expecting mothers who are concerned that the developing fetus may be affected by a genetic disorder. NT screening isn’t a blood test, but an ultrasound that is performed by a medical provider or OB/GYN between the 11th and 14th weeks of gestation. At this point in time, the fetus may exhibit extra levels of fluid near the nuchal fold, which is at the base of the neck.
A positive NT screening indicates that there is a possibility that the developing child may have an extra chromosome. This can be determined because the base of the neck is still transparent during this 3 week period of the pregnancy. The primary reason for this test is to determine if there is a chance a child may have Down Syndrome, but it can also be used to find heart defects and other genetic concerns.
Other screening tests, including blood tests, may accompany the ultrasound to help determine a specific diagnosis.
This Is a Test For Every Pregnant Woman
The ultrasound also serves a secondary purpose: to determine if the gestational age of the child has been measured correctly. The baby will be measured from the crown of the head to the rump and then the nuchal fold will be evaluated. A majority of children will not have excessive fluid in this fold during the NT ultrasound. If the measurements show the child is at the 15th week or beyond, then the NT test results may not be accurate.
If excessive fluid is shown to be present, then additional testing is typically ordered. This involves a CBS test and amniocentesis may also be necessary.
What Additional Tests May Be Ordered?
Some medical providers may order combined screening tests during the first trimester to track down the potential of a genetic disorder. Sometimes these tests are called the PAPP-A blod tests. The goal is to measure proteins and antibodies that may be present as different test results can indicate increased risks for heart issues, birth defects, genetic health issues, and even the chances of a premature birth.
The test results from this blood test are then combined with the NT ultrasound results to provide an expecting mother with a personalized risk assessment for the health of the developing child.
The NT screen can also be used with a second trimester test that measures four markers of possible genetic issues or birth defects. All of these blood tests may be ordered with the NT screen for a high risk pregnancy or none of them may be ordered if there are no concerns. Every pregnancy is different, so the need of additional testing beyond the ultrasound is at the discretion of the medical provider.
How Accurate Is the NT Screening?
Nuchal Transulency is not used to diagnose a specific condition. It only indicates that there is a higher than normal risk factor for chromosomal or genetic conditions. It is possible for an expecting mother to have abnormal test results on every test, yet have a child that is born perfectly healthy without defect at the scheduled time. It also means that normal test results will not guarantee that a child does not have a health issue that will need to be addressed at birth.
Normal test results to correlate with a lower risk of having a chromosomal or genetic disorder, however, when compared to abnormal results.
The accuracy of the NT screen is also dependent on the skill level of the medical provider that is conducting the test. Expecting mothers are recommended to receive this test at a specialized center instead of a general medical provider because of the skill level that is involved.
When the combined screening options are available, including the NT screen and blood testing, then first-trimester testing results can detect up to 80% of Trisomy 18 and Trisomy 21 disorders that have occurred. This allows parents to plan for having a child with special needs, secure resources if necessary, and locate support groups. There may be other options available as well depending on the jurisdiction that oversees where the parents live.
The odds of having a healthy baby are always in your favor. An abnormal result just means an increased risk. It isn’t a guarantee. Keep that in mind as you receive your nuchal translucency blood test results and you’ll be able to make an informed decision about your health needs.