Advanced analyses of the male partner: FISH technique on spermatozoa

Analysis of the chromosome set in spermatozoa. The FISH analysis technique can be used to detect abnormalities in the number of chromosomes in spermatozoa

What is FISH analysis?

FISH (fluorescent in situ hybridisation) analysis on spermatozoa is a technique that facilitates analysis of the genetic material in male gametes.

What is FISH analysis used for? What is the purpose of a FISH analysis?

FISH analysis of the ejaculate can help us to determine the quantity of spermatozoa that have an abnormal chromosomal set and to understand if they exceed normal levels.

Humans are a diploid species. In other words, we have two copies of each of the 23 types of chromosomes. Gametogenesis leads to haploid cells (eggs or spermatozoa) that contain only one copy of each chromosome. The gametogenesis process is not 100% efficient and there is a certain proportion of gametes with an abnormal number of chromosomes (aneuploidies). Problems arise when aneuploidy levels are high.

What does a FISH analysis entail?

A FISH analysis of spermatozoa consists of hybridisation using fluorescent probes on spermatozoa in ejaculate. These probes bind specifically to the chromosome for which they were designed (for example, chromosome 21) and, using fluorescence microscopy, it is possible to check whether the spermatozoa have the corresponding single copy of that chromosome or not.

In FISH spermatozoa analysis, five chromosomes are usually analysed: the X and Y sex chromosomes and chromosomes 13, 18 and 21. This analysis can be extended to cover other chromosomes if advisable based on the patient's medical background.

• Chromosomes 16 and 22 in cases of repeat pregnancy loss
• Chromosomes linked to abnormal karyotypes during the couple's previous pregnancies
• Chromosomes linked to the male partner's abnormal karyotype

When is a FISH analysis advisable?

A FISH analysis on sperm is recommended in couples with a background of recurrent pregnancy loss or implantation failure and in male partners with poor semen quality and abnormal karyotypes.

Patients with pathological FISH analysis in sperm are at a greater risk of having embryos with chromosomal abnormalities and a decreased ability to implant, pregnancy loss and the possibility of giving birth to children with abnormal karyotypes.

Where FISH analysis in sperm is abnormal, and if it is advisable based on the couple's medical background, comprehensive chromosome screening (CCS) can be used to select embryos with a correct number of chromosomes that will lead to a successful pregnancy and the birth of a healthy child.