PGT-A (Preimplantation Genetic testing for Aneuploidy)

(AKA Comprehensive Chromosome Screening CCS)


PGT-A is a breakthrough technology that can increase the success rate of IVF up to 70% in even high-risk patients.

PGT-A is a screening technique that is used with IVF to determine if an embryo contains a normal number of chromosomes. Healthy embryos should have 23 pairs of chromosomes. 

Anyone having IVF may benefit from PGT-A, but you might be particularly interested if you have had repeated miscarriages, failed IVF, or are over 36 years of age.

How Is PGT-A Different from Traditional IVF?

Typically, in IVF embryos are graded by their appearance. However, this is a bit like “judging a book by its cover” as there is no way of determining whether an embryo has the right number of chromosomes based on its appearance. PGT-A is a technique that lets us verify that embryos appearing normal are in fact chromosomally normal.

What Are the Advantages of PGT-A?

Selecting embryos that have been identified as normal with PGT-A can:

  • Increase pregnancy rates to 70% or more.
  • Reduce miscarriage rates to 5%-7%.
  • Minimize risks for chromosomal anomalies.
  • Allow chromosomally normal embryos to be frozen for future use.

What Are the Possible Outcomes of Embryos Tested by PGT-A?

Results will be relayed to you by a telephone call from one of the clinic doctors or genetic counselors. Details of the results for each embryo tested will be reviewed with you at this time and may include the following outcomes:

  • Normal chromosome number (euploid): These embryos have 46 chromosomes in each cell and are the best candidates for a successful transfer.
  • Abnormal chromosome number (aneuploid): These embryos have missing or extra whole or partial chromosomes in every cell and are likely to result in a miscarriage, failed transfer, or a baby with a chromosomal disorder.
  • Mosaicism: Embryos with a mosaic finding have some cells with a normal number of chromosomes and some cells with extra or missing whole or partial chromosomes. This result is less clear than the first two options.
    • If a normal euploid embryo is present, a mosaic embryo will not be transferred as they carry a higher rate of failed implantation and often end in early pregnancy loss.
    • Mosaic embryos with chromosomal abnormalities associated with known genetic syndromes, such as trisomy 21,13,18, are not recommended for transfer
    • Transferring any mosaic embryo is associated with uncertainty as to the possible health of the child
    • Consideration to the disposition of mosaic embryos is undertaken in consultation with your physician and after genetic counseling
  • Failed QC metrics or No Diagnosis: Results were unable to be obtained due to several possible issues. This occur in about 2% of biopsies. Embryo rebiopsy is offered.

What If an Embryo Has an Abnormal Number of Chromosomes?

If an embryo has too few or too many of any particular chromosomes, it could:

  • Fail to implant.
  • Result in a miscarriage.
  • Lead to offspring affected by conditions such as Down syndrome.

The probabilities of these outcomes increase with maternal age.

What are the steps in PGT-A?

Embryos created by IVF are grown up to the blastocyst stage (5 or 6 days after fertilization). A sample of about 5-10 cells are biopsied from the portion of the embryo destined to form the placenta. The inner cell mass, which will eventually form the baby, is not touched.

The embryos are frozen and remain at Olive, but cells are sent to a laboratory for genetic testing. The number of chromosomes for each embryo is analyzed with a technique called next-generation sequencing (NGS).


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Step 1

Mature eggs are removed from the ovary.

Step 2

The eggs are fertilized in the lab.

Step 3

Embryo cells divide.

Step 4

A blastocyst is biopsied at day 5, 6 or 7.

Step 5

DNA of 5-10 cells from the placental area are examined. Test results are returned within 10-14 days.

Step 6

Chromosomally healthy embryos are frozen for future transfer into the uterus.

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Is PGT-A More Expensive than Regular IVF?

As PGT-A requires several additional steps compared to traditional IVF, there is an increase in cost. However, many experts believe that the overall advantages of PGT-A, such as improved pregnancy rates and decreased miscarriage rates, will result in an overall cost benefit. It is also worth considering if patients would like more than one child, as they can have assurance of stored euploid embryos to implant at a later date instead of starting another IVF cycle at a later age. 

The Olive finance department will discuss the expenses in detail. 

Book an appointment to learn more about whether PGT-A is right for you.


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