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7 de March de 2024

FISH testing in sperm

FISH testing in sperm is an essential tool in assisted reproduction that analyzes the genetic material of sperm. Let’s explore what FISH is, when to use it, and what to do if the results show abnormalities.

What is FISH Testing?
Fluorescence In Situ Hybridization (FISH) is a cytogenetic technique that allows us to study the chromosomal characteristics of sperm.

This method uses fluorescent DNA probes that specifically bind to certain chromosomes. By observing them under a fluorescence microscope, we can determine how many copies of each chromosome are present in the sperm cells. Each chromosome is labeled with a different color, making it easy to count.

Sperm and eggs are the only human cells that contain half the number of chromosomes found in somatic (non-reproductive) cells—23 XX (for eggs) or 23 XY (for sperm).

With FISH, we can analyze how many copies of each chromosome are present in the sperm, identifying potential chromosomal abnormalities that may affect fertility and embryo viability.

Understanding Sperm Formation and Chromosomal Issues
The process of spermatogenesis (or gametogenesis) is how male germ cells develop into mature sperm through various stages of cell division and differentiation.

Spermatogenesis and Meiosis

Spermatogenesis begins with spermatogonia, which divide and differentiate into primary spermatocytes that undergo meiosis.

These primary spermatocytes undergo two rounds of cell division, resulting in secondary spermatocytes and finally haploid spermatids. The spermatids then undergo morphological changes and DNA packaging to form mature sperm ready for fertilization.

Risks of Chromosomal Abnormalities
During meiosis, errors can occur, leading to sperm with an abnormal number of chromosomes, known as aneuploidies. These chromosomal abnormalities can cause fertility issues, miscarriages, or genetic disorders in offspring.

Typically, five chromosomes are studied during FISH: three somatic chromosomes (13, 18, and 21) and the two sex chromosomes (X and Y). These may show duplications, deletions, or other anomalies, although additional chromosomes can be tested if needed.

Generally, about 1,000 sperm from a sample are analyzed to provide a diagnosis.

Since gametogenesis is not 100% efficient, there will always be a percentage of sperm that have an altered chromosome number. The issue arises when the percentage of abnormal sperm exceeds that of a control population, indicating a quality problem.

FISH testing helps detect these chromosomal abnormalities and assess their impact on fertility and the viability of embryos in assisted reproduction treatments.

When Should FISH Testing Be Done?

FISH testing may be recommended for:

  • Men with an abnormal karyotype
  • Men who have undergone chemotherapy or radiation therapy
  • Older men
  • Men with low semen quality, such as oligozoospermia (low sperm count) or teratozoospermia (low percentage of normally shaped sperm)
  • Previous IVF cycles with implantation failure or embryo arrest
  • Cases of recurrent miscarriages
  • Prior pregnancies with chromosomal disorders
  • Unexplained infertility
  • By detecting chromosomal abnormalities, informed decisions can be made regarding assisted reproduction treatments and embryo selection to improve success rates in IVF procedures.

FISH Testing Procedure

The FISH procedure involves several precise steps:

  • Preparation of the sperm sample on a slide.
  • Hybridization of specific fluorescent probes with the chromosomes of interest.
  • Observation under a fluorescence microscope to detect signals from the probes on the chromosomes.
  • Analysis and counting of the signals to determine the presence of chromosomal abnormalities.
  • Impact of FISH on Fertility Treatments
  • FISH testing has shown significant benefits in improving implantation rates and success in IVF. It allows for the identification of genetically healthy sperm, increasing the chances of achieving a successful pregnancy.

Strategies for Enhancing Conception Odds with FISH

This personalized approach, based on the genetic evaluation of sperm, facilitates the detection and exclusion of those with chromosomal abnormalities, maximizing conception options in assisted fertility treatments.

What If My FISH Results Are Abnormal?

For patients with a normal karyotype but abnormal FISH results, the outlook for IVF cycles may not be favorable, as there may be a higher number of chromosomally abnormal embryos.

This situation can result in lower implantation rates, higher miscarriage rates, and an increased risk of live births with chromosomal abnormalities.

Each case should be evaluated individually, but generally, couples with abnormal FISH results are guided toward undergoing IVF with Preimplantation Genetic Testing (PGT). This method improves implantation rates and reduces miscarriages.

  • Preimplantation Genetic Testing (PGT) in the Context of FISH
  • Preimplantation Genetic Testing (PGT) plays a crucial role in selecting healthy embryos after sperm examination using FISH. This technique enables the identification and exclusion of embryos with chromosomal abnormalities, increasing the chances of successful fertilization and embryo development.

Thanks to PGT, embryos with chromosomal anomalies can be identified and discarded, improving the likelihood of achieving a successful pregnancy and reducing the risk of miscarriages or complications during gestation.

Recommendations and Follow-Up After FISH Analysis

Tips for Couples Who Have Undergone FISH Testing
After undergoing FISH testing, it’s essential for couples to follow some recommendations to optimize their chances of success in assisted reproduction treatments:

  • Seek emotional support and share experiences with other couples in similar situations.
  • Maintain open and honest communication about the test results and available options.
  • Follow medical advice and attend all necessary follow-up appointments.
  • Monitoring and Counseling for Detected Chromosomal Abnormalities
  • If chromosomal abnormalities are detected in sperm, it’s crucial for couples to receive specialized follow-up and counseling to make informed decisions:
  • Consult a genetic specialist to assess the impact of chromosomal abnormalities on fertility and potential inheritance.

Explore treatment options such as PGT to select healthy embryos before transfer.
Receive guidance on available assisted reproduction options and any ethical or legal implications.

FIVIR Clinic: Consultation and Follow-Up with Assisted Reproduction Specialists

If you’re uncertain about your chances of conception as a couple, seeking specialized care from IVF professionals is vital.

At Instituto FIVIR, we specialize in assisted reproduction. We evaluate your case individually to determine the best treatment options and follow-up.

We offer various assisted reproduction techniques tailored to your needs. Our services include FISH testing, artificial insemination with donor eggs, IVF with donor eggs, and preimplantation genetic testing.

Contact us for more information! We're here to help you on your journey to parenthood.

 

Everything you need to know about fertility

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