Preimplantation Genetic Testing (PGT)
Preimplantation Genetic Testing (PGT) is a procedure in which embryos created during an IVF cycle are tested for genetic abnormalities prior to being transferred to the patient’s uterus. An embryologist uses a laser to take a very small sample from a blastocyst-stage embryo. The sample is analyzed by a specialized laboratory and the results provide information about the health of the embryos, helping the physician choose the healthiest embryo to transfer to the uterus to achieve pregnancy.
PGT fits within the IVF process as follows:
- During an IVF cycle, embryos are created by retrieving the eggs from the female patient’s ovaries and fertilizing them with sperm in the IVF laboratory. The embryos are cultured in the laboratory and allowed to develop for 5-7 days until they reach the blastocyst stage.
- Using a laser, the embryologist takes a small biopsy sample of cells from the trophectoderm, which is the outer layer of the blastocyst that will later develop into the placenta.
- After the embryos have been biopsied, they are frozen and safely stored within our IVF laboratory at our Mount Kisco location. Meanwhile, the biopsied samples are sent to an outside laboratory that specializes in PGT.
- It can take approximately 1-2 weeks for the results to come back. Some PGT tests require more time to complete.
- After the results are provided, your doctor and/or a genetic counselor will review the results to help choose which embryo to use for transfer. At this point, we can also schedule an embryo transfer appointment.
Our facility offers patients three types of PGT:
- PGT-Aneuploidy (PGT-A)
- PGT-Monogenic Conditions (PGT-M)
- PGT-Structural Rearrangements (PGT-SR)
Preimplantation Genetic Testing for Aneuploidy (PGT-A), formerly known as preimplantation genetic screening, or PGS, is used to screen embryos for chromosomal abnormalities.
Found in the nucleus of every animal and plant cell, chromosomes are threadlike structures of tightly wound DNA. Chromosomes are passed from parents to their offspring through female and male gametes (eggs and sperm). Humans are born with 23 pairs of chromosomes; we receive 23 chromosomes from our mother and 23 chromosomes from our father, which comes to a total of 46 individual chromosomes.
Chromosomes play a crucial role in the replication and distribution of DNA during cell division. However, during this process, errors sometimes occur at random, resulting in cells having extra or missing chromosomes. This phenomenon is known as aneuploidy. Trisomy is the most common aneuploidy and occurs when there is an extra chromosome. Down syndrome is a common trisomy (trisomy 21). The risk of having a child with aneuploidy increases as a woman ages. Aneuploidy typically results in implantation failure, miscarriage, or the live birth of a baby with physical or intellectual disabilities.
PGT-A reduces these risks by identifying the healthiest embryo for transfer, thereby increasing the likelihood of a healthy pregnancy and baby. The doctors of RMA of New York at CareMount have extensive experience using the results of PGT-A to help many patients achieve their dreams of having a family, while experiencing fewer obstacles on their journey.
PGT-Monogenic Conditions (PGT-M)
Preimplantation Genetic Testing for Monogenic Conditions (PGT-M), formerly known as Preimplantation Genetic Diagnosis, PGD, is utilized in situations where the patient(s) are already aware of the possible presence of a specific genetic disorder. Before attempting conception, patients and partners are recommended to undergo expanded carrier screening to determine whether they are at risk for passing a specific genetic disorder on to their offspring. If they are found to be a Carrier Couple, PGT-M can be performed on an embryo prior to transfer to determine which embryo is most likely to result in a healthy child. Monogenic disorders are genetic disorders caused by mutations in a single specific gene. This knowledge can come from a known family or personal medical history, carrier screening, and/or previous genetic testing. The goal of PGT-M is to identify and use only embryos that are free of the inherited condition.
PGT-M can take months to complete due to the elevated level of screening needed to ensure that the risk of passing a genetic abnormality onto your child is mitigated. PGT-A can be completed concurrently with PGT-M if desired by the patient or advised by a doctor. Performing PGT-M prior to embryo transfer can greatly reduce the risk of having a child with a specific genetic disorder.
PGT-Structural Rearrangements (PGT-SR)
Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) is recommended for individuals who are carriers of a balanced translocation or inversion. In these instances, carriers have the correct number of chromosomes, but there are small segments of chromosomes that are duplicated, deleted, or rearranged. Although most carriers are healthy, they are prone to creating embryos with extra or missing chromosome segments, which increases the risk of miscarriage. PGT-SR is used to identify embryos with the correct amount of chromosome material, in order to transfer the healthiest embryos, and greatly improve the chances of a successful IVF cycle and healthy pregnancy.
Limitations of Preimplantation Genetic Testing
As with any form of medical screening, there are limitations patients will need to note when considering PGT. Although the accuracy of detecting abnormalities is high (about 97-99%, depending on the type of genetic test), it is not 100%. False positives and false negatives can occur.
Furthermore, there are some rare types of genetic abnormalities and conditions that may not be detectable by PGT-A or PGT-SR tests. As for PGT-M tests, they can only detect the conditions that are being targeted by the probe test. PGT tests are unable to screen for disorders that are without an identifiable genetic cause (e.g. spontaneous birth defects, cerebral palsy, autism, etc.). As such, your doctor may suggest prenatal genetic testing as a follow-up. This would be completed via your obstetrician with assistance from a genetic counselor.
Choosing RMA of New York at CareMount for PGT
Since 2001, RMA of New York has successfully facilitated the births of thousands of healthy babies for patients across the New York City metro area and beyond. By combining RMA of New York’s world-renowned expertise in reproductive care with CareMount’s long-standing commitment to delivering local exceptional care, we’re able to offer that same personalized, state-of-the-art fertility care right in your Hudson Valley neighborhood. We provide the expertise, technology, research, resources, and compassion needed to help ensure your future family is in the best of hands. No matter the path needed to complete your family-building goals, you can count on our team to be in your corner every step of the way.
To learn more about PGT with RMA of New York at CareMount, please:
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