The genetic material of a sperm cell is organised into 23 chromosomes, although there are instances when this number is altered for various reasons and can generate embryos with an abnormal number of chromosomes.
What is FISH testing?
FISH (Fluorescence in situ hybridization) is a genetic diagnostic technique used to determine whether sperm’s chromosome endowment is correct. This technique allows us to evaluate the risk of transmitting chromosomal abnormalities of paternal origin to the resulting embryo.
Why are FISH tests administered?
Testing allows specialists in reproductive medicine to advise couples which is the most appropriate assisted human reproduction treatment in order to achieve pregnancy.
What happens in the event of an altered result?
If an altered result is obtained, embryos will require a genetic analysis in order to select those chromosomally normal. This type of treatment is known as preimplantation genetic diagnosis (PGD).
Does performing this technique avoid other genetic studies?
No. FISH is a useful diagnostic test at the foundation of genetic counselling, but it does not exclude additional tests which medical professionals may consider necessary.
Once the semen is analysed by FISH, can normal sperm be used for IVF?
No. The FISH technique is a diagnostic procedure which analyses what proportion of spermatozoa are altered and therefore permits greater understanding and genetic advice.
When is this technique required?
There are different groups of patients which yield a higher percentage of chromosomally-altered sperm:
- Patients with seminal alterations: a low sperm count (oligozoospermia), inactivity (asthenozoospermia), or altered morphology (teratozoospermia) may suggest genetic alterations in sperm.
- Patients with altered meiosis: when meiosis (the process of sperm formation) is not executed correctly it can lead to chromosomally-altered sperm. The study of meiosis is carried out by means of an outpatient test: testicular biopsy.
- Patients with repeated miscarriages: when two or more miscarriages are induced spontaneously, it may be a symptom of genetic alteration.
- Patients with failures in IVF (in vitro fertilisation).