Pre-genetic Testing (PGT)

What is Pre-genetic Testing?

Preimplantation genetic testing (PGT) is a procedure used to help identify genetic defects within embryos created through in vitro fertilisation (IVF) before pregnancy. PGT involves removing one or more cells from an IVF embryo to test for specific genetic conditions. 


Who is suitable for PGT?

  • Couples who have a known genetic disorder in their family and want to avoid passing it on to their children.
  • Couples who have experienced recurrent pregnancy loss, which might be due to chromosomal abnormalities in the embryos.
  • Women of advanced maternal age (usually over 35), as the risk of chromosomal abnormalities in embryos, increases with maternal age.
  • Couples where the woman has experienced repeated IVF failure, which could be due to chromosomal abnormalities in the embryos.
  • Couples where one or both partners have a known chromosomal rearrangement.
  • People who want to use donor eggs or sperm and want to ensure the embryos' genetic health.


PGT is a complex procedure that has ethical considerations and potential risks. Before proceeding, it should be discussed in depth with a fertility specialist. Also, PGT does not guarantee a successful pregnancy or a healthy baby; it is a tool that can increase the chances of a successful pregnancy and reduce the risk of having a child with a specific genetic disorder.


Benefits of Pre-genetic Testing

  • Reduced Risk of Genetic Disorders: If you or your partner are carriers of a genetic condition or have a family history of a certain disease, PGT can help reduce the risk of passing these on to your children.
  • Increased Chance of Successful Pregnancy: For couples who have experienced multiple miscarriages or failed IVF attempts, PGT can help identify embryos more likely to result in a successful pregnancy and healthy birth.
  • Informed Decision-Making: PGT can provide valuable information about your embryos' genetic health, allowing you and your doctor to decide which embryos to transfer.
  • Reduced Need for Prenatal Diagnostic Testing: Since PGT is performed before implantation, it may reduce the need for invasive prenatal diagnostic procedures (like amniocentesis or chorionic villus sampling), which carry a small risk of miscarriage.


Types of Pre-genetic Testing

  • PGT-M (for Monogenic/Mendelian disorders): This is used when parents have a known genetic disorder that they risk passing on to their children. It tests for specific single-gene disorders.
  • PGT-SR (for Structural Rearrangements): This is used when one or both parents have a chromosomal rearrangement, such as translocations or inversions.
  • PGT-A (for Aneuploidies): This is used to detect embryos with an abnormal number of chromosomes, which can lead to conditions like Down syndrome or can cause miscarriage.


Alternative Options to Pre-genetic Testing

  • Prenatal Diagnostic Testing: Procedures such as amniocentesis and chorionic villus sampling can be used to detect genetic abnormalities after pregnancy has occurred.
  • Adoption or Foster Care: Adopting or fostering a child may be a preferred option for some people.
  • Donor Eggs or Sperm: Using eggs or sperm from a donor with no known genetic disorders can be an option.
  • Natural Conception with Postnatal Testing: Some couples may choose to conceive naturally and utilise postnatal testing for any suspected genetic disorders after the child is born.
  • Preimplantation Genetic Haplotyping (PGH): This method is similar to PGT but checks for genetic markers surrounding a gene rather than the gene itself.
  • Lifestyle Changes and Risk Management: For some genetic conditions, certain lifestyle changes or treatments can help manage the condition.


Pre-genetic Testing Prognosis

When PGT results successfully identify healthy embryos for transfer, this can significantly increase the chance of a successful pregnancy and reduce the risk of having a child with a specific genetic disorder. However, it's important to note that PGT does not guarantee a successful pregnancy or a healthy baby, and miscarriages can still occur.


Complications and Risks of Pre-genetic Testing

  • Misdiagnosis: While PGT is generally accurate, there is a small chance of misdiagnosis. This can happen if the cells removed from the embryo for testing are not representative of the whole embryo (mosaicism) or due to technical errors.
  • Damage to the Embryo: There's a very small risk that the procedure used to remove cells from the embryo for testing can damage it, potentially preventing it from developing further.
  • False Positives/Negatives: The test can produce false positives (indicating a problem where there isn't one) or false negatives (failing to detect a problem that is present).
  • Ethical and Emotional Considerations: Deciding what to do with embryos that test positive for genetic disorders can be a difficult and emotional process. Some people may have ethical concerns about selecting embryos based on genetic characteristics.
  • Multiple Pregnancies: If more than one embryo is transferred, there's a risk of multiple pregnancies, which can increase health risks for both mother and babies.
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