How & When is PGT Performed
Preimplantation Genetic Testing (PGT) is performed by sampling the developing egg or embryo at the appropriate time points during an In Vitro Fertilization (IVF) cycle.
Reproductive Genetic Innovations customizes the testing strategy to obtain the most accurate diagnosis for a patient’s embryos. Our scientists and genetic counselors work with you and your physician to determine the optimal testing plan for each individual case, based on individual needs in concert with the doctor’s recommendation. The testing strategy chosen will determine which biopsy type is best.
Blastocyst / Trophectoderm Biopsy
A blastocyst is an embryo that has developed to the Day 5 —6 stage and will contain around 100 cells.
Blastocyst biopsy involves the removal of a small number of cells from the outer layer, known as the trophectoderm. Blastocyst testing typically requires that embryos are cryopreserved (frozen) after biopsy. They are then tested at RGI to determine embryos to transfer. Later they are thawed for the transfer (FET) by the clinic. This biopsy method and testing provides optimal accuracy for diagnosis of single gene disorders (PGT-M) and/or 24 chromosomes testing for aneuploidy (PGT-A).
Innovative No Laser assisted Trophectoderm Biopsy
Innovative “N0 Laser” assisted Trophectoderm Biopsy is performed by RGI’s embryologists on day 5 of human embryo development for diagnosis of Single Gene Disorders (PGT-M) and/or 24 chromosomes testing for aneuploidy (PGT-A).
Next-Generation Sequencing is a method in which the DNA sequence of the embryo biopsies is directly analyzed. This is used primarily to identify if there are extra or missing copies of chromosomes. This testing may sometimes detect smaller pieces of duplicated or deleted chromosomal material. The optimal accuracy is obtained when performed on blastocyst (day 5/6) embryo biopsy.
Developments in Next-Generation Sequencing for chromosomal rearrangements (PGT-SR) is used for detection of rearranged translocated fragments no smaller than 4-5 Mbp. The method detects not only unbalanced embryos, but also allows identifies aneuploid embryos. A special family-specific design is used for distinguishing balanced from normal embryos. For smaller fragments, a different design is required, which should be discussed in advanced.
Can be performed by request. A Blastomere is an embryo that has developed to the Day 3 (cleavage) stage.
Blastomere biopsy involves the removal of one cell from the developing embryos for diagnosis of single gene disorders (PGT-M) and/or 24 chromosomes testing for aneuploidy (PGT-A). Results of blastomere testing are typically available in time for a Day 5 transfer in the same IVF cycle.
Polar Body Biopsy
Can be performed by request. Polar bodies are the by-products of egg division. Polar bodies arise during early cell design (Meiosis) in the oocyte, being extruded at the time of fertilization. They would naturally degrade; however, they can be removed and tested to deduct the genetic status of the oocyte (egg) fertilized. Polar body testing only tests for the maternal genetic contribution to the embryo and occurs at the Day 0 and/or Day 1 stage.
Both polar bodies must be removed and tested in order to make an accurate diagnosis, and therefore, fertilization of the egg is necessary. For couples in which discarding fertilized embryos is not an option, cryopreservation (freezing) can occur prior to the fusion of the egg and sperm nuclei (2PN stage). Results of polar body testing are typically available in time for a Day 3 or Day 5 transfer in the same IVF cycle. This Biopsy type is rarely used today.
The patient should NOT start IVF stimulation medications until the PGT setup is complete. RGI will contact the IVF center (and the patient) once the PGT setup is complete. Setup cannot be started until RGI has completed patient counseling, processed necessary paperwork (such as a HIPAA form, consent documents, financial agreements/clearance, and other paperwork) as well as received necessary DNA samples. We ask that the IVF center and patient’s keep RGI informed of medication start dates such as stimulation start dates and hCG administration.
PGT results are typically ready within 7 to 10 business days and are reported directly to the IVF physician. Once results are understood, the process of embryo selection can determine which are most suitable for transfer and implantation. Embryos remain cryo-preserved and available for future embryo transfer.
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Patients pursuing PGT-M for a single gene condition or PGT-SR for a translocation/chromosomal rearrangement should provide a copy of their genetic reports.
An RGI Board Certified Genetic Counselors will review the PGT process during a consultation with the patient and will coordinate the necessary paperwork and samples to get started. Genetic Counseling is necessary for every PGT-M, PGT-SR and PGT-HLA patient, consulting is recommended for PGT-A patients as well. Counseling is provided at no extra cost to patients by our licensed genetic counselors, available to discuss prenatal testing options with your patients and help guide them every step of the way.
Patients undergoing single gene testing will receive a DNA Collection Kit containing all necessary materials for PGT setup. If deemed necessary by our lab, a kit may be sent for patients undergoing translocation/inversion testing. This will be determined during the review of reports.
PGT-M setups for single gene cases take 3-6 weeks for common conditions, and up to 8 weeks for complex cases. Setup for translocation/inversion cases take 3-5 weeks, although a setup for such cases is not typically required.
ICSI is required for all PGT cases.
Intracytoplasmic Sperm Injection (ICSI) is a method of artificial feralization preferred for ALL preimplantation genetic testing, including single gene and aneuploidy testing.
Patients can contact RGI directly to get started. Medical providers are able to send referral information through the PGT requisition form prior to the start of an IVF cycle.
The PGT Requisition form must be completed by the IVF center once the patient has been calendared for their cycle. It is to be determined between the patient and IVF physician which type of biopsy and PGT testing plan is appropriate for the patient.
Reproductive Genetic Innovations has been performing PGT-M since its inception in 1989, and remains one of the most active centers offering preimplantation genetic testing in the world. RGI also offers testing for all 24 chromosomes, using Next-Generation Sequencing, having state-of-the-art technologies to test all the chromosomes. Our scientists were the first to develop a strategy for preimplantation genetic testing for single genes that is optimized for HLA matching.