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Preimplantation Genetic Testing (PGT)

Preimplantation Genetic Testing (PGT) is an advanced reproductive technology used in the in vitro fertilization (IVF) process to screen embryos for genetic abnormalities before they are transferred to the uterus. PGT helps select embryos free from specific genetic disorders, chromosomal abnormalities, or aneuploidies, enhancing the likelihood of a successful pregnancy and reducing the risk of genetic diseases in offspring..

Embryo biopsy for preimplantation genetic testing

When is Preimplantation Genetic Testing (PGT) Done?

Preimplantation Genetic Testing (PGT) may be recommended in various scenarios to individuals or couples undergoing in vitro fertilization (IVF) treatment. Here are some common situations in which PGT may be recommended:

  • Women aged 35 and older face a higher risk of chromosomal abnormalities in their eggs, increasing the chances of miscarriage and genetic disorders. PGT-A (Aneuploidy Screening) is recommended to screen embryos for chromosomal normalcy, enhancing the likelihood of a successful pregnancy.

  • Couples experiencing multiple miscarriages may undergo PGT to detect embryos with chromosomal abnormalities or genetic issues causing miscarriages. PGT-A or PGT-M (Monogenic Disorder Screening) may be advised depending on the circumstances.

  • Couples with severe male factor infertility, including low sperm count, poor motility, or abnormal morphology, might opt for PGT to reduce the risk of passing on genetic abnormalities. PGT-A helps in selecting embryos with the highest chances of successful implantation and pregnancy.

  • Couples with known genetic disorders like cystic fibrosis, sickle cell anemia, Huntington's disease, or chromosomal rearrangements may choose PGT-M or PGT-SR (Structural Rearrangement Screening) to identify and select unaffected embryos, reducing the risk of transmitting genetic disorders to their offspring.

  • Couples who have had multiple unsuccessful IVF cycles or recurrent implantation failures may consider PGT to uncover potential reasons for treatment failure. PGT-A can help identify embryos with chromosomal abnormalities, providing guidance for future treatment strategies.

TYPES OF PGT

Preimplantation Genetic Testing (PGT) includes several genetic screening methods during the IVF process to assess embryos for specific genetic abnormalities or chromosomal disorders.

PGT-A (Aneuploidy Screening):

Screens embryos for aneuploidies, or abnormal numbers of chromosomes, which can lead to conditions like Down syndrome and are common causes of implantation failure, miscarriage, and chromosomal disorders.

PGT-M (Monogenic Disorder Screening):

Detects specific genetic mutations or monogenic disorders, such as cystic fibrosis, sickle cell anemia, or Huntington's disease, allowing at-risk couples to select unaffected embryos.

PGT-SR (Structural Rearrangement Screening):

Used for couples with structural chromosomal rearrangements, such as translocations or inversions, increasing miscarriage or chromosomal abnormalities risk. PGT-SR identifies embryos with balanced chromosomal structures.

PROCEDURE OF PGT

Pregnancy Testing and Follow-Up:

  • About 10-14 days after embryo transfer, a blood test measures beta-hCG levels to determine pregnancy.

  • If positive, ongoing monitoring and follow-up with a fertility specialist or obstetrician are conducted to monitor the pregnancy's progress.

Ovarian Stimulation and Egg Retrieval:

  • Ovarian stimulation involves hormonal medications to stimulate multiple egg production.

  • The woman’s response is monitored through ultrasound scans and hormonal blood tests.

  • A trigger shot of human chorionic gonadotropin (hCG) induces final egg maturation.

  • Eggs are retrieved approximately 36 hours later using a minimally invasive transvaginal ultrasound-guided procedure.

Fertilization and Embryo Culture:

  • Retrieved eggs are fertilized with sperm using either conventional insemination or intracytoplasmic sperm injection (ICSI).

  • Embryos are cultured in a laboratory incubator for 5-6 days until they reach the blastocyst stage.

Embryo Biopsy:

  • At the blastocyst stage, a small number of cells are biopsied from each embryo for genetic analysis.

  • The biopsy can be performed by removing cells from the trophectoderm or at the cleavage stage using specialized micromanipulation techniques.

Genetic Analysis:

  • Biopsied cells are analyzed using techniques such as polymerase chain reaction (PCR), fluorescent in situ hybridization (FISH), array comparative genomic hybridization (aCGH), or next-generation sequencing (NGS).

  • PGT-A analyzes chromosomal content for aneuploidies.

  • PGT-M detects specific genetic mutations or monogenic disorders.

  • PGT-SR identifies chromosomal rearrangements.

Embryo Transfer:

  • Genetically normal embryos are selected based on PGT results and transferred to the woman’s uterus using a thin catheter.

  • Remaining viable embryos may be cryopreserved for future use.

SHOULD YOU GO FOR PGT ?

If you have a known genetic disorder or a family history of genetic conditions, and are undergoing IVF treatment, adding PGT is highly recommended. This step can prevent passing on genetic disorders to your offspring. PGT is also recommended in cases of infertility issues where egg or sperm quality is compromised, increasing the chances of successful fertility treatment.

FAQ’s

    • PGT is a technique used during in vitro fertilization (IVF) to screen embryos for genetic abnormalities before they are transferred to the uterus. It helps select embryos free from specific genetic disorders, chromosomal abnormalities, or aneuploidies.

    • PGT is recommended for couples with a history of genetic disorders, recurrent pregnancy loss, advanced maternal age, severe male factor infertility, or those who have experienced multiple unsuccessful IVF cycles.

    • By screening for genetic and chromosomal abnormalities, PGT allows for the selection of the healthiest embryos, reducing the risk of miscarriage and genetic disorders, and increasing the likelihood of a successful pregnancy.

    • PGT-A (Aneuploidy Screening): Screens embryos for chromosomal abnormalities.

    • PGT-M (Monogenic Disorder Screening): Detects specific genetic mutations.

    • PGT-SR (Structural Rearrangement Screening): Identifies chromosomal structural rearrangements like translocations and inversions.

    • PGT is highly accurate, but no test can guarantee 100% accuracy. It significantly reduces the risk of transferring embryos with genetic abnormalities.

    • Yes, PGT is performed using advanced techniques that minimize the risk to the embryos. The biopsy usually involves removing a few cells from the embryo without harming its development.

    • The cost of PGT varies depending on the clinic, location, and specific tests performed. It is advisable to consult with the fertility clinic for detailed pricing.

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