What is Preimplantation genetic testing (PGT)?
Preimplantation genetic testing (PGT) is a cutting-edge procedure used to identify genetic abnormalities in embryos created with in vitro fertilization (IVF). The goal of PGT is to allow your physician to select embryos predicted to be free of a specific genetic condition or chromosome abnormalities for transfer. This test provides patients with an opportunity to reduce the chance for a genetic disease in their future children prior to pregnancy.
How does PGT work?
If you are interested in PGT, the first step is to notify your physician. Determining whether you should have PGT performed for your embryos is a complex decision so careful discussion with your physician is important. We also strongly recommend genetic counseling for all our patients who are considering PGT. Like all genetic tests, PGT has important benefits and limitations of which patients should be aware. The decision to have PGT needs to be made well in advance of your IVF cycle.
If PGT is part of your plan, you will need to undergo an IVF cycle to retrieve eggs and create embryos. The embryos are monitored in our laboratory until day 5 or 6 after fertilization when they are referred to as blastocysts. At that point, a small number of cells are removed from each embryo and shipped to an outside laboratory for PGT. The Fertility & Reproductive Center partners with several reference laboratories that perform PGT.
While PGT is being performed on the DNA from the cells that were removed, the embryos are cryopreserved (frozen) and stored in our laboratory. Once the PGT results are available, typically in 1-2 weeks after the biopsy, you will be notified of the results. If you have embryos that are appropriate for transfer, you will schedule a frozen embryo transfer with your physician.
Biopsy being performed on an embryo at the blastocyst stage. Typically, 5-10 cells are removed for genetic testing.
Screening for chromosome abnormalities (PGT-A and PGT-SR)
PGT can also evaluate an embryo’s chromosomes, the structures in every cell that contain our genes. It is not uncommon for embryos have random chromosome abnormalities such as missing or extra chromosomes, also known as aneuploidy. These chromosome abnormalities happen by chance and are not typically inherited from a parent or donor. Embryos with aneuploidy are more likely to result in a miscarriage or failed IVF cycle. Less commonly, aneuploidy may result in the birth of a child with a chromosome condition such as Down syndrome (trisomy 21).
In a typical IVF cycle, embryos are chosen for transfer based on their appearance under the microscope. The embryo’s appearance can give us some indication of its potential to result in a successful pregnancy, but it is not perfect. Preimplantation genetic testing for aneuploidy (PGT-A) provides additional information about the reproductive potential of the embryos and may help select the best embryo for transfer. PGT-A is most often considered for patient who have had recurrent pregnancy losses (miscarriages), multiple unexplained failed IVF cycles, a prior pregnancy or child with certain chromosome abnormalities, or based on maternal age. While PGT-A can be performed for any IVF cycle, there are both benefits and limitations that should be carefully discussed with your physician to determine if PGT-A is right for you.
One final type of PGT called PGT-SR is for structural rearrangements. This type of PGT is performed when a patient or their partner has a rearrangement of their own chromosomes such as a translocation or inversion. A person with a structural rearrangement of their own chromosomes is at increased risk to produce embryos with missing or extra pieces of chromosomes. Embryos with missing or extra pieces of chromosomes are more likely to result in a miscarriage or a child with serious health issues.
What does preimplantation genetic testing test for?
Preimplantation genetic testing can test for over 400 different single-gene disorders, including cystic fibrosis, sickle cell anemia, Tay-Sachs, and Huntington’s disease.
What is the process of preimplantation genetic testing?
Preimplantation genetic testing involves testing the early embryo after in vitro fertilisation, thus allowing replacement into the uterus of unaffected embryos.
Is PGT a testing worth it?
For patients over 37, PGT-A can dramatically increase pregnancy rates. Still, for women under 37, this may not significantly increase their chances of conception. Each fertility clinic’s track record with PGS/PGT-A and PGD will give patients better insight into if PGS/PGT-A is a risk to their embryos.
What is the cost of PGT?
The cost per embryo of PGT-A is about 10,000 to 15,000, which is roughly about 10 to 15 per cent of the IVF cycle. With PGT-A the chances of a successful pregnancy are doubled, and the patient is saved the financial, physical, and emotional trouble of another IVF cycle.”
Who is PGT suitable for?
PGT may be recommended by your doctor if you: Are known to carry a genetic or chromosomal condition. Are of advanced maternal age (> 35 years). Have had repeated, unsuccessful attempts with IVF, ICSI and / or FET.
How common is PGT-A?
Modern PGT-A methods are not very common, as it is used to detect abnormalities of IVF.
Does PGT a test for gender?
In addition to detecting gender PGT a can also detect chromosomal abnormalities, PGT-a can also identify the sex chromosomes of an embryo and identify the gender. It is often used to help with family balancing or to help families avoid gender specific genetic diseases or conditions.