Nuchal Translucency Testing

A new option is available for the early detection of chromosomal abnormalities, called 1st trimester screening, which can be done at 11-12 weeks of gestation.

We are certified by The Fetal Medicine Foundation to provide this procedure (we earned this certification and have been performing this test since 2005!)

The Nuchal Translucency Screening Test consists of an ultrasound and a blood test, which we schedule at 11-12 weeks gestation.

The ultrasound examines an area on the back of the neck of the fetus, called the nuchal translucency (NT). If the NT is enlarged (too wide), this can be a sign of possible Down syndrome or other anomaly.

The blood test involves obtaining just a few drops of blood from the fingertip. The Nuchal Translucency Screening Test results allow us to recalculate the patient’s risk for Down syndrome. The new risk is often lower than the risk calculated using the mother’s age. The new risk becomes the basis for decision-making.

Decision Making

For example: A 35 year-old pregnant woman has a 1/276 risk of Down syndrome based on her age. This is also the age where genetic testing (e.g. amniocentesis) would normally be offered. If the Nuchal Translucency Screening Test is done, the new risk might be much lower than 1/276 (say 1/500), so that a decision can be made NOT to have the amniocentesis. Alternatively, if the new risk is higher, say 1/200, then it might an easier decision to have the genetic testing done.

Using the Nuchal Translucency Screening Test we can detect about 80 to 90% of all cases of Down syndrome. Unfortunately, this means that some patients will have normal results and ultimately might still deliver a baby with Down syndrome. On the other hand, we can advise many women not to have an amniocentesis, saving them from the possible risk of miscarrying a normal pregnancy (about 2-4 per 1000 amnios).

Does not test for Spina Bifida

Note that the Nuchal Translucency Screening Test does not screen for spina bifida (neural tube defects). Also, if the results are abnormal, it is too early for amniocentesis, so a CVS test may be warranted, which carries with it a slightly higher risk of miscarriage.

The use of first-trimester screening is becoming more popular, but is not yet the standard of care. If someone does the Nuchal Translucency Screening Test, there is disagreement over whether or not the 16-week afp blood test still needs be done, so we still advise having the afp test.

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