What is a fish in a cvs test?

FISH is an acronym for "fluorescence in situ hybridization". Basically, it is a way to get faster preliminary results to your CVS testing. It is not the full results...they just fluoresce the main chromosomes that they want to look at: 21, 18 & 13 and the sex chromosome. From this, they will be able to tell you whether there is an abnormality on any of those chromosomes. The rest of the results take about two weeks--so the FISH results are welcome information that you do not have to wait so long for. I had this done and got my FISH results back the next day with no abnormalities found. Still waiting for the rest of the results, but definitely feel better.