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What Is a Nuchal Translucency?

Many tests are given to expectant mothers to ensure a healthy well being for their baby. It is common that, along with these tests, there are follow-up procedures to make sure the results are accurate. These tests are also given to detect early problems in the fetal development, so early intervention can be taken if possible. Sadly, sometimes a decision needs to be made whether to keep a child that may possibly have health problems---a decision that is a sensitive one and totally up to the parents.

  1. Definition

    • Nuchal translucency is a "sign" seen and documented by the ultrasound technician typically during an ultrasound examination of the fetus. This ultrasound technician does not discuss the finding, but will report it to the doctor by documentation and images with measurements to support the finding. The term itself refers to the measurement of fluid in the nuchal region in the back of the neck. Measurements larger than in the normal range are associated most often with Down Syndrome or Trisomy 21.

    Associated Signs/Symptoms

    • Other symptoms are visible sometimes during the ultrasound exam that accompany the nuchal translucency. These are the " lemon head sign," which is a skeletal anomaly involving the skull shape that can be recognized as a lemon-shaped appearance of the skull rather than the classic round appearance. Measurements taken routinely of the femur, the long bone of the thigh, will be appear shorter than average as well. This would be the same case with the bones of the arm. A bright appearance of the bowel in the abdomen may also be observed as gastrointestinal defects are common in babies with Down Syndrome.

    Time Frame

    • The exam is done between 11 to 13 weeks of pregnancy during an ultrasound. Between these weeks is the best time to check for nuchal translucency. This test is used to see if further testing is needed. It is not a diagnosis. During the test, the fluid located behind the neck region of the fetus is measured. The measurement is compared to the Crown Rump Length measurement of the fetus to see if the measurement is within normal limits. Sixty to 85 percent of fetuses with Down Syndrome will have an enlargement of this measurement.

    Risk Factors

    • Women over the age of 35 who become pregnant are more at risk of having a baby with Down Syndrome. The risk is about a one in 400 chance. If the woman is over 40, the risk increases by almost four times. Genetics also play a role in the chances of having a child with Down Syndrome, if others in the family were born with the condition.

    Follow Up

    • There are follow-up tests such as Amniocentesis or Chorionic Villus Sampling. CV sampling is done early between the weeks of 10 and 12. Amniocentesis is done at a later time between the weeks of 16 and 20. These can confirm the condition by sampling the DNA and screening for the chromosomal abnormality present with Down Syndrome. Additional blood tests may also be ran to confirm and rule out other disorders.

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