Preimplantation Genetic Testing (PGT)
Reduce your time to pregnancy.
About Preimplantation Genetic Testing (PGT)
Preimplantation Genetic Testing (PGT) can test embryos created with in vitro fertilization (IVF) before they are transferred into the uterus for pregnancy. There are different types of PGT: PGT-A, PGT-SR and PGT-M.
Preimplantation Genetic Testing for Aneuploidy, screens embryos for chromosomal abnormalities or aneuploidy. Chromosomes are found in the centre of our cells and in the cells of a developing embryo. Chromosomes are important because they provide important information and instructions telling our cells how to function. Usually there are 46 chromosomes in the cells of an embryo, 23 chromosomes from the oocyte and 23 chromosomes from the sperm. Embryos with chromosomal aneuploidy are less likely to implant and can result in miscarriage or birth of a child with a chromosomal disorder. Embryos with the usual number of chromosomes in their cells have the highest chance to result in implantation and successful pregnancy.
PGT-A uses next generation sequencing (NGS) technology to analyze the chromosomes in the cells of the embryo with the aim of selecting embryos with the correct number of chromosomes for transfer. PGT-A may reduce the chance of miscarriage and may allow you to have a successful pregnancy with fewer embryo transfers.
Anyone can choose to have PGT-A completed as part of their IVF cycle. The more common indications for PGT-A include:
- The oocyte provider is older than 35 at time of retrieval
- Previous IVF treatments that were unsuccessful or resulted in miscarriage
- There is a history of recurrent miscarriage - usually more than 1
- They have a child or a previous pregnancy with a chromosomal disorder
Preimplantation Genetic Testing for Structural Rearrangements is used to screen embryos for specific chromosomal abnormalities when either the person providing the oocyte or the person providing the sperm has a chromosomal rearrangement, such as a translocation or inversion, in their cells. If the oocyte or sperm provider has a chromosomal rearrangement, their embryos have a higher chance to have chromosomal abnormalities. As with PGT-A, PGT-SR uses NGS technology to assess all the chromosomes in the embryo cells, with the goal of selecting embryos without chromosomal abnormalities for transfer. PGT-SR may lower the chances of experiencing a miscarriage and reduce the time it takes to have a healthy pregnancy.
Indications for PGT-SR include:
- The person providing the oocyte or the sperm has a known chromosomal rearrangement, such as a balanced translocation or inversion
Preimplantation Genetic Testing for Monogenic disorders is used to test embryos for specific single-gene genetic disorders. The goal of PGT-M is to provide patients at risk to have a pregnancy or child with a genetic disorder the opportunity to have a pregnancy or child that is unaffected with the genetic disorder.
Indications for PGT-SR include:
- There is an increased chance to have a child affected with a single-gene (monogenic)genetic disorder)
- The oocyte and sperm providers are carriers for a single-gene genetic disorder
- There is a family history of a single-gene genetic disorder
- The oocyte or sperm provider is affected with a single-gene genetic disorder
Your PGT Journey Begins Here
PGT is an add-on to an IVF cycle and eliminates the possibility of doing a fresh embryo transfer after IVF. Therefore, those using PGT should expect to delay the embryo transfer after an IVF cycle by as much as two months. Results from genetic testing will vary depending on the test. Expect to wait x weeks for several weeks for PGT-A results. PGT-M and PGT-SR can extend the process by several months as the genetics lab needs to develop special probes.
Attend a PGT-A webinar
Join the LIVE PGT-A webinar hosted by one of our Genetic Counsellors. This webinar is free for our patients. Ask your clinical coordinator for details.
Make a decision about PGT ad inform your Clinical Coordinator
If you wish to proceed with PGT-A in your IVF cycle, your clinical coordinator will arrange for you to sign the required consent forms and facilitate the PGT-A testing.
In-depth Discussion with Genetic Counsellor
If you are considering PGT-M or PGT-SR, a consultation with a genetic counsellor is required to provide you with information about the testing and help you decide about proceeding with the testing. With PGT-M and PGT-SR, the genetics team will work closely with the PGT reference lab (CooperGenomics) to confirm that PGT-M or PGT-SR can be used to test your embryos. This must happen before you can start your IVF cycle to make embryos.
For PGT-M, the Test Development with the PGT lab can take up to 3 months to complete and may require samples from other family members.
Development of Genetic Probes for PGT-M and PGT-SR Only (3-4 months)
If you are considering PGT-M or PGT-SR, it typically takes some time 3 to 4 months to develop probes to be used in testing. These are developed based on your specific genetic traits.
PGT-A does not require the development of probes and therefore is a much shorter process.
Complete an IVF Cyce
Genetic testing of embryos occurs only after a completed IVF cycle. Please refer to the process of IVF for more information on what is involved to retrieve and fertilize eggs. Once we have blastocyst embryos, we can begin the process of genetic testing.
Embryo Biopsy
Embryos are biopsied at blastocyst stage, usually 5-6 days after fertilization. The embryologist will remove a few cells from the outer part (trophectoderm) of the embryo and ship the biopsied cells to the PGT lab for analysis. The embryos are then frozen on-site and can remain frozen until embryo transfer.
Results Discussion
PGT results are reported approximately 2-3 weeks after embryo biopsy. Our Genetic Counsellor will contact you when the results are received and arrange a review of the results. Following a review with the Genetic Counsellor, you will meet with your physician to make a plan for embryo transfer.
Embryo Transfer
The final step in a PGT cycle is to transfer an embryo that has been tested an analyzed for genetic abnormalities.
Genetic Testing Services Provided by Markham Fertility Centre
Preimplantation Genetic Testing (PGT)
After IVF, testing of an embryo to help eliminate those with genetic abnormalities.
Prenatal Screening
During pregnancy to identify whether your baby is more or less likely to have certain birth defects.