Nuchal Translucency Screening
Nuchal translucency screening is a diagnostic ultrasound imaging test designed to provide information about a fetus's health. It is used to measure the size of the clear space in the tissue at the back of the fetus's neck that is known as the nuchal translucency. Although every fetus has some fluid at the back of the neck, a fetus with certain chromosomal abnormalities tends to have a much larger amount. The increased amount of fluid causes the clear space to be measurably thicker. During nuchal translucency screening, the mother is given a blood test, which also helps to establish whether the fetus has a chromosome disorder.
Nuchal translucency screening detects whether there is an elevated risk for genetic conditions such as Down syndrome. When the back of the fetus's neck is thicker than usual, it may be an indication of a chromosomal abnormality. A nuchal translucency test is recommended based on various factors, including the age and health of the mother, and whether there is a family history of Down syndrome or other chromosomal abnormalities.
The Nuchal Translucency Screening Procedure
Nuchal translucency screening is usually performed between the 11th and 14th weeks of pregnancy. The mother is first given a blood test, which also helps determine the fetus's risk for Down syndrome or other chromosomal abnormalities. Once the blood is drawn, it is sent to a separate lab for analysis.
A nuchal translucency screening is typically performed abdominally. Gel is applied to an area of the lower abdomen, and an ultrasound device is gently placed against the skin to obtain an image. In other cases, a transvaginal technique may be necessary. It involves the insertion of a slim, baton-like ultrasound device into the vagina. Both methods produce images that enable the doctor to clearly see and measure the nuchal translucency space at the back of the fetus's neck.
When the results of a nuchal translucency screening become available, the doctor assesses the risk of the fetus's having a chromosome disorder. If the results are in the normal range, the risk of Down syndrome is very low. If the results are in the abnormal range, further testing will likely be recommended to determine what condition, if any, the fetus has.
Considerations of Nuchal Translucency Screening
Nuchal translucency screenings are optional. As the chance of giving birth to a child with chromosomal abnormalities increases with age, many pregnant women older than 35 elect to undergo the test as a precaution. However, even positive results do not mean that a child will be born with Down syndrome or a chromosomal abnormality, and further testing is often required for confirmation.