If you want a lot of medical information on the test, I'd "google" it and check it out. But, I can tell you that several of us here have had it done. It's basically a screening test for chromosomal problems. An ultrasound is done that measures the fluid at the nuchal fold (back of the neck). This can be an indicator of Down Syndrome and a couple other chromosomal abnormalities. The thicker the fold, the higher the risk that there's a problem. Normally the test is combined with other measurements from the ultrasound, and with the results of a blood test from the mother. With these measurements, the mother is given a risk factor. For example, I think my Down Symdrome risk factor was something like 1:500, meaning that there was a 1 in 500 chance my baby has DS. Keep in mind that this is just a RISK factor - it's not definitive. If you want to know for SURE, the amniocentesis or Chorionic Villus Sampling will give you a definate yes or no. Many people choose the Nuchal Translucency test to guide them, as it's much less invasive and there's no risk (as there is with the amnio or CVS). Good luck with whatever test you decide to get!