Preimplantation Genetic Testing (PGT)

Preimplantation Genetic Testing

Preimplantation Genetic Testing (PGT) is a form of genetic testing used to look for specific genetic disorders in embryos. It is performed on the cells of a biopsy taken from the embryos at approximately 5-7 days of growth (the blastocyst stage). There are two types of PGT:

Preimplantation Genetic Diagnosis (PGD)

PGD looks for specific genetic disorders for which we know the embryos are at risk because of previous genetic testing of the parents or a known family history. There are 3 main indications for PGD:

Recessive Disorder
  • Both the patient and partner are carriers for the same recessive disorder (Cystic Fibrosis, Spinal Muscular Atrophy and Gaucher disease are a few examples).
  • 25% chance of having an affected child.
  • Usually picked up on preconception carrier screening OR from a couple having an affected child and then being tested.
Dominant Disorder
  • One of the two parents is affected with a dominant disorder (BRCA1/2, NF1 and Polycystic Kidney disease are a few examples).
  • 50% chance of having an affected child.
  • All testing will be from an outside geneticist as these types of disorders are not on carrier screening.
X-linked Disorder
  • The female partner is a carrier for an X-linked disorder.
  • 25% chance of having an affected son and 25% chance of a having a carrier daughter.
  • Usually picked up on carrier screening.

The couple, therefore, must have undergone genetic testing already to determine the exact disorders for which their embryos are at risk AND the exact type of mutation (or gene change) involved. This is typically done either via carrier screening (for recessive or X-linked diseases) or outside testing with a geneticist if one of the parents is actually affected with a genetic disorder (dominant diseases). Once that information is known, PGD requires approximately 2 months of prep work with an outside laboratory (a PGD lab) before treatment in order to create a specialized test (also called a “probe”) specific to the couple’s combination of mutations and genetic markers; DNA samples from the couple’s parents and other relatives are sometimes required as well in order to create an accurate test.

While the couple waits for the results to come back, embryos are cryopreserved and stored in RMA of NY’s embryology lab. This prep process is facilitated as a joint effort between RMA’s Genetic Counselor, the couple’s IVF Coordinator, and the PGD lab. RMA of NY works with several PGD laboratories, including Foundation for Embryonic Competence (FEC), Natera, Good Start Genetics, Coopergenomics, and RGI. Typically whichever PGD network is in network with the couple’s insurance (if any) is used. However, there are some cases where an out of network lab may be needed because of a specific clinical indication that the in-network laboratory cannot test for.

Preimplantation Genetic Screening (PGS)

PGS looks for extra or missing chromosomes (the structures that hold all our genes) in the embryos. This type of genetic issue is usually not inherited and can happen randomly in the eggs or sperm of both women and men at any age, although chromosome abnormalities do occur more frequently in the eggs of women over 35 years of age. PGS does not require any specialized prep work with a PGD lab and is recommended for all couples undergoing an IVF cycle as it greatly reduces the chances of failed implantation or miscarriage. Most patients undergoing PGD for a specific gene disorder also request PGS concurrently to make sure that any embryos that are free of the disease in question are also chromosomally viable. PGS may sometimes be medically indicated – and, thus, possibly covered by insurance – if there is a history of recurrent pregnancy loss and/or if one member of the couple has a balanced translocation or another chromosome rearrangement.

Why RMA of New York: Preimplantation Genetic Testing

RMA of New York offers patients personalized, compassionate, and premium fertility care. As the Division of Reproductive Endocrinology and Infertility of Mount Sinai Hospital, our team is dedicated to scientific discovery, graduate medical education, and patient-focused care. We are proud to be a member of the Department of Obstetrics, Gynecology, and Reproductive Science at the Icahn School of Medicine at Mount Sinai and of recognition as a Center of Excellence by US News & World Report.

To learn more about PGT at RMA of New York, please contact us, or make an appointment.

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