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What is PGT-A?

Updated: Aug 6, 2022

Today on my YouTube channel, Katie Lee CGC Talks Miscarriage and Fertility I discussed Preimplantation Genetic Testing for Aneuploidy (PGT-A).


Check out my video here: https://www.youtube.com/watch?v=fcAyb3scR8I


WHAT IS PGT-A:

PGT-A stands for Preimplantation Genetic Testing for Aneuploidy.

  • P stands for Preimplantation. With PGT-A an embryo is tested before it is transferred/implanted into a uterus. This means that the embryo is created outside of the body by joining sperm cell and egg cell together in a lab during or after an IVF cycle. If the egg is fertilized and an embryo is created, a small sample of cells can be biopsied from the embryo for this testing. The PGT-A results help the patient and doctor determine the next steps in fertility treatment and which embryo to implant into the uterus.

  • GT stands for Genetic Testing. PGT-A is a type of genetic testing examining the chromosomal makeup of the embryo.

  • Aneuploidy is the scientific term for an abnormal number of chromosomes.

    • Chromosomes are the structures that hold our genetic makeup or DNA. Most people have 46 chromosomes, making them chromosomally typical. The scientific term for an embryo with 46 chromosomes is euploid. Euploid embryos are those that are standardly recommended for transfer. Embryos that are euploid (chromosomally normal) have 46 chromosomes and are most likely to result in a liveborn baby.

    • Any deviation from having 46 chromosomes is known as aneuploid. Embryos that are determined to be aneuploid with PGT-A are less likely to implant into the uterus and result in a healthy baby than embryos that are euploid. An example of an aneuploidy is Down syndrome which is also known as trisomy 21. People with Down syndrome have 47 chromosomes instead of 46. Specifically, they have three copies of chromosome 21 instead of the more typical pair of chromosome 21. There are many individuals living with Down syndrome on our planet, but embryos with Down syndrome are more likely to miscarry than embryos that are euploid with 46 chromosomes. Most types of aneuploidy cause an embryo not to implant in the uterus ro to miscarry very early in pregnancy. A handful of aneuploidies including trisomy 21/Down syndrome can result in ongoing pregnancies and liveborn babies with differences due to the extra or missing chromosome.


Other names that can be used for PGT-A are PGS (Preimplantation Genetic Screening) or CCS (Comprehensive Chromosome Screening). These terms are used interchangeably by most providers.


WHY UTILIZE PGT-A?:

  • A chromosomally normal sperm or egg cell will have 23 chromosomes. When a sperm cell with 23 chromosomes and an egg cell with 23 chromosomes join to form an embryo the embryo will have 46 chromosomes. There is a chance that any sperm or egg cell could have a chromosome imbalance and that it could lead to a chromosomally abnormal embryo. Even when the egg source and sperm source are perfectly healthy with no family history of genetic diseases, there is a chance that they could have a child or an embryo with a missing or extra chromosome.

  • Chromosome imbalances (aneuploidy) can cause the embryo to fail to implant or can lead to miscarriage. Some imbalances cause chromosome syndromes like Down syndrome. Some individuals wish to reduce the risk of transferring an embryo with a chromosome imbalance.

  • Many providers recommend PGT-A if the egg source is 35 or older. The chance of having chromosome imbalances increases significantly as females/ individuals with eggs age.


HOW DOES IT WORK?:

  • PGT-A is performed on embryos that are created in the laboratory. This typically involves an egg retrieval or the thaw of frozen eggs which are then fertilized by sperm that are collected with masturbation or with a surgical procedure if necessary.

  • Three to eight cells from a 100-150 cell embryo are biopsied and shipped to a specialty laboratory to perform genetic testing. The embryo does not need to be shipped to perform the testing. The biopsy does not have to be returned to the embryo and is typically saved by the laboratory for a period of time and then discarded. The laboratory issues a genetic test report with the PGT-A results to the doctor who ordered the test. The results are used by the physician and patient(s) to determine the next steps for treatment.


WHO IS PGT-A FOR:

  • PGT-A is typically available for any patient regardless of age (as long as embryos will be created outside of the body).

  • Speak with your doctor is you are good candidate for PGT-A and IVF


IN SUMMARY:

PGT-A is a screening test that can be utilized by individuals who are undergoing an IVF cycle or planning to transfer frozen embryos into the uterus. PGT-A is used to distinguish chromosomally normal (euploid) embryos from chromosomally abnormal (aneuploid) embryos.


It is important to know that PGT-A is not a perfect test. PGT-A relies on a small sample from each embryo. There is a chance that the biopsy may not represent the rest of the embryo or that the test results may be incorrect. Some IVF doctors recommend PGT-A for most of their patients and other physicians are critical of PGT-A and treat most patients without the test. If you have questions about whether PGT-A can improve your IVF success, I would encourage you to speak with multiple IVF doctors to determine the best step for your treatment.


This content is for educational and informational purposes only. Please contact your doctor or another qualified healthcare provider with any questions you may have regarding medical advice, your condition, or treatment.



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