pre-implantation genetic testing

What must you know about preimplantation genetic testing when going through IVF and should you consider it? We talk with Rachael Cabey, a Licensed Certified Genetic Counselor and a lead laboratory genetic counselor for Cooper Genomics and Jenna Miller, a Licensed Certified Genetic Counselor and a clinical science liaison for Cooper Genomics. Jenna travels around the US educating clinicians about genomics and genomic testing.

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Hit the Highlights
  • Understanding the terms.
    •  Pre-2019
      • Preimplantation Genetic Testing (PGT)
      • Preimplantation Genetic Screening (PGS)
      • Preimplantation Genetic Diagnosis (PGD).
      • Current Terminology
        • PGS is now Preimplantation Genetic Testing for Aneuploidies (PGT-A).
        • PGD is now Preimplantation Genetic Testing for Monogenic/Single-Gene Disorders (PGT-M)
        • Preimplantation Genetic Testing for Chromosomal Structural Rearrangements (PGT-SR)
  •  PGT-A
    • What is PGT-A?
    • Aneuploidy can cause what adverse outcomes?
    • How many chromosomes can be screened for?
    • Who should consider having this testing?
    • What can PGT-A show us?
      1. Whole Chromosomal that are extra or missing.
      2. Difficult to detect a balanced translocation.
      3. What is a Polyploidy?
      4. Segmental aneuploidy? Smaller deletions or duplications
  • Because the missing or extra piece of chromosome is less severe than a whole extra or missing chromosome, segmental aneuploidies have a higher chance or resulting in a child born with physical or intellectual disabilities.
  • What do we mean by the resolution of the testing?
  • Is it possible to determine from which parent (the egg or sperm) the chromosome abnormality originated? Why might this be important?
  • What are the different testing platforms that can be used with PGT-A?
    • Next Generation Sequencing (NGS)
    • Single NucleotidePolymorphisms (SNPs)
  • Mosaicism
    • What is mosaicism? (the presence of a mixture of chromosomally normal and abnormal cells)
    • Not related to maternal age. Occurs after fertilization.
    • Are there different degrees of mosaicism?
    • Does the presence of mosaicism impact the implantation rate, miscarriage rate, and birth defect rate?
  • What does the research show on how PGT-A impacts the success rate of IVF?
    • How is the test performed?
    • How accurate is PGT-A testing? What is the risk of false negatives and false positives?
  • Preimplantation Genetic Testing for Monogenic/Single-Gene Disorders (PGT-M)
    • What is PGT-M? (looks for specific inherited conditions controlled by a single gene)
    • Alternative options
    • Who should consider having this testing?
    • Does PGT-M impact the success rate of IVF?
    • Does this testing process differ from PGT-A?
    • How accurate is PGT-M testing?
  • Preimplantation Genetic Testing for Chromosomal Structural Rearrangements (PGT-SR)
    • What is PGT-SR?
    • Who should consider having this testing?
    • Does this testing process differ from PGT-A or PGT-M?
    • How accurate is PGT-SR testing? Same range mid to high 90%
  • Important Additional Information
  • Patients and health care providers should be aware that a “normal” or negative preimplantation genetic test result is not a guarantee of a newborn without genetic abnormalities.
  • Importance of genetic counseling.
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Music credit: Michael Ashworth

Photo credit:  Gerd Altmann from Pixabay