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How accurate is a Nuchal fold test?
Q: I just turned 41 and am expecting my first child in October, with much joy. I am scheduled for a Nuchal Translucency test next week and I'm not familiar with the test's percentage of accuracy. If it comes out normal, I am not sure if I should stop there or still have an amniocentesis. The baby's father is 50 this year. Neither one of us have a history of any birth defects. He has one child who is now 18. I don't smoke, drink or take any drugs and am basically quite healthy, just very concerned about having a Down's baby at our age. What are the odds of the test coming out normal and not being correct?
A: Dear Trena,

Nuchal fold or Nuchal Translucency testing involves performing an early ultrasound, between the 11th—14th weeks of pregnancy, to look at the back of the baby's neck. Researchers in England have found that the wider the space, the greater the risk of having a child with a DNA problem. Performing a set of blood tests at the same time will increase the accuracy of the test.

Most doctors will tell you that the test identifies 90% of babies with a problem; ten percent of the time, the test will not discover the problem. In the United Kingdom, the Nuchal fold test is the only test offered to determine if an amniocentesis is warranted. However, in the United States, it is still considered experimental and an amniocentesis is the recommended test. I am sure your obstetrician has reaffirmed this with you.

Personally, I inform patients about the availability of the test. I also explore a patient's attitude and hesitancy about performing an amniocentesis. Ultimately, the decision to proceed with testing is left to the family. To date, I have had many patients have the Nuchal fold test with excellent results; I have also had one test that missed a Down syndrome pregnancy.

Trena, you have to ask yourself some pretty difficult questions. You have approximately a 2% risk of having a child with a chromosomal problem. Your good health and your husband's prior healthy child don't really enter into the equation. The risk is purely based upon your age (not too much related to your husband's age). The risk of losing your child from an amniocentesis is .5%. You might want to speak with a genetic counselor to help find the right answer for you.

Craig L. Bissinger M.D.