How Pre-implantation Genetic Testing (PGT) Boosts IVF Success?

In Vitro Fertilization (IVF) is a well-known assisted reproductive technology that has brought joy to countless couples struggling with infertility. However, even with IVF, achieving a successful pregnancy can sometimes be challenging due to genetic abnormalities in embryos. This is where Pre-implantation Genetic Testing (PGT) comes into play. PGT is an advanced technique that screens embryos for genetic disorders before implantation, significantly improving the chances of a successful pregnancy. This blog will delve into the details of PGT, its benefits, the process involved, and answer some frequently asked questions.

Understanding Pre-implantation Genetic Testing (PGT)

What is PGT?

Pre-implantation Genetic Testing (PGT) is a procedure used to identify genetic defects in embryos created through IVF before pregnancy. It involves taking a biopsy from the embryo and analyzing it for chromosomal abnormalities or specific genetic conditions. This ensures that only genetically normal embryos are selected for transfer to the uterus.

Types of PGT:

• PGT-A (Pre-implantation Genetic Testing for Aneuploidies): This test screens embryos for abnormal numbers of chromosomes, which can lead to conditions like Down syndrome, Turner syndrome, and other chromosomal abnormalities.

• PGT-M (Pre-implantation Genetic Testing for Monogenic/Single Gene Defects): This test identifies specific genetic disorders caused by mutations in a single gene, such as thalassemia, cystic fibrosis, sickle cell anemia, and Huntington’s disease.
• PGT-SR (Pre-implantation Genetic Testing for Structural Rearrangements): This test detects structural rearrangements in chromosomes, such as translocations and inversions, which can cause genetic disorders or affect embryo viability.

What are Mosaic Embryos?

Mosaic embryos are embryos that contain both normal and abnormal cells. This condition, known as mosaicism, occurs when some cells within the embryo have the correct number of chromosomes while others do not. During the early stages of embryonic development, errors in cell division can lead to this mixture of chromosomally normal and abnormal cells. Mosaic embryos can present a unique challenge in IVF because their potential to develop into a healthy pregnancy is uncertain. However, advances in genetic testing have made it possible to identify and analyze mosaic embryos, providing valuable information for making informed decisions about their use in IVF treatment.

The Process of PGT in IVF

Step-by-Step Process:

• Ovarian Stimulation and Egg Retrieval: The IVF cycle begins with the woman undergoing ovarian stimulation using hormone medications. The goal is to stimulate the ovaries to produce multiple eggs.Once the eggs are mature, they are retrieved from the ovaries using a minor surgical procedure called follicular aspiration.

• Fertilization: The retrieved eggs are then fertilized with sperm in a laboratory dish. This can be done through conventional insemination (placing sperm near the egg) or through Intracytoplasmic Sperm Injection (ICSI), where a single sperm is injected directly into an egg.

• Embryo Culture: Fertilized eggs (now embryos) are cultured in a controlled laboratory environment. The embryos are monitored for their development and progression.

• Embryo Biopsy: At around day 5-6 of development, when embryos typically reach the blastocyst stage (consisting of about 100 – 300 cells), a few cells (usually 5-10) are carefully removed from each embryo. This process is known as embryo biopsy and is performed using specialized techniques to ensure minimal impact on the embryo.

• Genetic Analysis (PGT): The biopsied cells are sent to a genetic laboratory where they are analyzed to detect genetic or chromosomal abnormalities.

• Embryo Selection:Based on the results of the genetic analysis, embryos that are determined to be chromosomally normal (or free of the specific genetic disorder being screened for) are selected for transfer. This helps maximize the chances of a successful pregnancy and reduces the risk of miscarriage.
• Embryo Transfer:The selected embryo(s) are transferred into the woman’s uterus. This procedure is typically done 5-7 days after fertilization, depending on the stage of embryo development.The number of embryos transferred depends on various factors, including the woman’s age, embryo quality, and the clinic’s protocols.

Benefits of PGT in IVF

• Increased success rates: By selecting embryos free from genetic abnormalities, PGT significantly increases the chances of a successful pregnancy and reduces the risk of miscarriage.

• Reduction in miscarriages: Chromosomal abnormalities are a common cause of miscarriage. PGT helps identify and avoid transferring embryos with these abnormalities, thereby reducing the risk of miscarriage.

• Lower risk of genetic disorders: PGT allows for the detection of specific genetic conditions, ensuring that only embryos without these disorders are selected for transfer. This reduces the risk of genetic diseases in the baby.

• Enhanced pregnancy outcomes: By transferring only genetically screened embryos, PGT can lead to better pregnancy outcomes, including higher implantation rates and healthier pregnancies.

Candidates for PGT

Who should consider PGT?

• Couples with a history of genetic disorders.

• Women of advanced maternal age. (over 35 years)

• Couples with repeated IVF failures or recurrent miscarriages.

• Couples with a history of chromosomal abnormalities.

• When either partner has chromosomal translocation

Criteria for PGT Eligibility: Your fertility specialist will assess your medical history, genetic background, and specific circumstances to determine if PGT is appropriate for you.

Risks and Limitations of PGT

Potential Risks:

• Embryo biopsy is a delicate procedure and carries a small risk of damaging the embryo.

• Genetic testing is highly accurate but not infallible. There is a small chance of approx (2%) of false positives or negatives.

• PGT may not detect all genetic abnormalities.

• There is a possibility that embryo may self correct any abnormalities, although not definitely proven

Limitations and Considerations:

• PGT is an additional step in the IVF process and adds to the overall cost.

• Not all embryos will be suitable for biopsy and testing.

• Ethical and emotional considerations regarding the fate of non-selected embryos.

• PGT is a method of screening & selection of available embryos, if there are very less suitable embryos for transfer PGT may not improve success chances.

Conclusion

This comprehensive guide should help you understand how Pre-implantation Genetic Testing can improve IVF success rates. If you have more questions or need personalized advice, consult with your fertility specialist. For more information or to schedule a consultation, please contact Bavishi Fertility Institute today.

For personalised advice tailored to your test results and diagnosis, book a consultation with our specialists at Bavishi Fertility Institute.