Preimplantation Genetic Diagnosis (PGD)
The Institute for Reproductive Medicine and Science at Saint Barnabas has, since its inception in 1995, been a world-wide leader in the development and application of diagnostic genetic technology specifically designed to for human embryos. Many of the procedures that are currently used in all advanced IVF centers were developed or refined at IRMS. Today, IRMS and its scientists and physicians continue to improve the state of the art in PGD, both by technical innovation and by demonstrating with clinical successes the full potential of PGD to aid a wide variety of patients to have normal, healthy pregnancies and deliveries.
Dr. Santiago Munne, Ph.D. has been a central figure in PGD field since the early 1990’s. He has led the PGD effort at IRMS since 1995, and he continues today, as the Director of Reprogenetics LLC, to provide leadership and expertise. Reprogenetics is composed of a team of scientists and counselors dedicated to providing the highest level of Preimplantation genetic diagnosis, in all of its forms. The scientists and physicians of IRMS work closely with the Reprogenetics staff on a daily basis to coordinate the treatment of all of our PGD patients.
Each year, hundreds of patients who are at risk for producing embryos with specific genetic abnormalities are treated at IRMS. The basic PGD procedure involves embryo biopsy – the removal of a single cell from an embryo on Day 3 of development – and then testing it for genetic abnormalities. The embryo biopsy is performed by IRMS embryologists, and then fixed on site by Reprogenetics scientists. The fixed cells are then taken to the Reprogenetics laboratory in Livingston for analysis. Results are typically available within 24 hours; the embryos that are determined to be chromosomally and/or genetically normal are then transferred on Day 4.
This centralized process allows us to maximize the chance of success for our patients. Each of the steps in the process is performed by an expert, and results made are available so quickly that embryo transfer on Day 4 is usually possible. For some embryos, transfer on Day 4 confers a significant advantage over transfer on later days.
Who benefits from PGD?
PGD testing may be appropriate for couples with:
- Advanced maternal age (>36)
- Experience of repeated miscarriage
- Experienced repeated IVF failure
- Previously pregnancy with a chromosomal abnormality
- Risk of passing a genetic disorder on to their children
- Risk of having children with a particular X-linked disorder
- A partner who carries a balanced chromosomal translocation
There are three basic types of genetic analysis performed at IRMS
- Chromosomal aneuploidy
Chromosomal aneuploidy refers to an abnormality of chromosome number within the cells of the embryos. Normal embryos should inherit one copy of each chromosome from each parent and therefore have two copies of each chromosome. Occasionally, chromosomal irregularities arise due to errors that occur during cell division. These types of errors occur more frequently in older patients. Aneuploid embryos are unlikely to lead to a successful pregnancy, and couples at risk of producing aneuploid embryos may experience infertility. Aneuploidy testing screens for common chromosome irregularities (involving chromosomes X, Y, 13, 15, 16, 18, 21 and 22). This testing may be appropriate for:
- Couples with advanced maternal age (>36)
- Couples who have experienced repeated miscarriage
- Couples who have experienced repeated IVF failure
- Couples who have previously had a pregnancy with a chromosomal abnormality
- Chromosomal translocations
Chromosomal translocations involve rearrangement of the chromosomal material. Individuals who are carriers of a translocation may experience difficulty with reproduction because they are producing chromosomally unbalanced embryos. The translocation may be the cause of difficulty conceiving, or may result in miscarriage after conception. For translocation patients, probes are developed that are specific for the chromosomes involved in the translocation. The test will be able to distinguish between normal or balanced embryos (which have the potential to produce a healthy baby) and unbalanced embryos (which would either fail to implant, miscarry, or give rise to an affected baby).
- Single gene disorders
Single gene disorders are genetic conditions caused by the alteration or mutation of a specific gene located on one of the chromosomes. Single gene disorders are inheritable. Individuals who are affected by one of these disorders, or who have a family history of a genetic disorder, may be at risk for passing the condition onto their children. Examples of some of the more common single gene disorders include cystic fibrosis, sickle cell anemia, Fanconi anemia, Tay Sachs disease, and Fragile X syndrome. Even rare gene disorders may be assessed with this technology, provided the causative gene is known.
Preimplantation genetic testing for a single gene disorder after IVF makes it possible to distinguish between genetically normal and affected embryos. In this way, it is possible to know whether an embryo is unaffected with a genetic condition prior to the establishment of pregnancy. PGD can be employed to dramatically reduce the risk of having a child with a serious genetic disorder.
For Further information on PGD, please visit the links below: