Fluorescent In Situ Hybridization (FISH) of sperm is a complementary test for the study of male fertility. It is a cytogenetic technique that uses fluorescent DNA probes to mark specific chromosomes in sperm. The aim of FISH is to identify whether the chromosome endowment of the sperm is correct.
Usually, the FISH technique is used to analyze chromosomes 13, 18, 21, X and Y, since these are the chromosomes that usually have the most alterations. However, FISH can also be used for other chromosomes.
A normal FISH result would show only one signal for each chromosome. On the other hand, an altered FISH would correspond to the visualization of several signals for the same chromosome.