Preimplantation Genetic Diagnosis and Screening


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Preimplantation Genetic Diagnosis and Screening (PGD/PGS)

These cutting edge technologies allow embryos to be tested for various genetic (Cystic Fibrosis), or chromosomal conditions (such as Down syndrome) prior to implantation in couples who are under-going IVF.

Since the birth of the first IVF baby, doctors, scientists, patients and ethicists have realized with a mixture of excitement and skepticism that combining the emerging technologies of IVF and genetics could allow for the screening of genetic conditions prior to conception. Over the past few years, this dream has become a reality through Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS).

PGD/PGS can be used to detect three types of conditions. The primary use of PGS is to screen for an abnormal number of chromosomes, known as aneuploidy. Down syndrome is a well-known example of this problem. As women mature, they produce larger numbers of eggs with aneuploidy, so that after age 40, over 50% of the eggs/embryos derived from the woman may have aneuploidy. Additionally, inherited chromosome translocations can be detected through PGS. A translocation occurs when two chromosomes exchange pieces. A person who carries a balanced translocation has an increased risk to have offspring with unbalanced chromosome rearrangements that can cause physical and mental abnormalities or result in multiple miscarriages.

The primary use for PGD is to test for certain single gene disorders, such as cystic fibrosis, Tay-Sachs disease, and sickle cell anemia and avoid transmission of these genetic diseases to one’s offspring.

PGS is accomplished by applying fluorescent probes for specific genes or chromosomes, to a single cell taken from the early embryo. Results of PGS are available in two days, and only those embryos that are chromosomally normal are transferred into the uterus on the third or fifth day after egg retrieval. PGD, while also requiring the removal of a cell from the embryo, applies specific probes onto the genes to diagnose the presence or absence of the specific disease in question.

By eliminating embryos with genetic or chromosomal abnormalities, the chance of achieving a healthy pregnancy increases; embryos with chromosomal abnormalities would either not implant in the uterus, result in an early miscarriage, or lead to a pregnancy with abnormalities. Women aged 34 and over are offered aneuploidy screening, because the proportion of eggs that are chromosomally abnormal increases with a woman’s age. For couples carrying single gene disorders, PGD can allow them to have a healthy baby without having to undergo prenatal testing and possible pregnancy termination.

Couples planning to undergo IVF who are interested in learning more about PGD/ PGS first need to consult with a genetic counselor, who will review their family history and risk factors. HRC has a genetic counselor who can explain PGD/PGS in more detail and help couples explore their options.

HRC Fertility Rancho Cucamonga is proud to announce an affiliation with Natera, a more complete way of bringing PGD into mainstream diagnostics. This is the first commercially available test to leverage bioinformatics to inform IVF transfer decisions by identifying potential abnormalities across all 24 chromosomes from a single embryonic cell. Test results are available within 24 hours and have a accuracy rate exceeding 99% for the cell tested.

This new technology uses genetic information from both the mother and father – obtained via a simple cheek swab – as well as data from the Human Genome Project, to create an accurate reconstruction of the genetic makeup of each embryo prior to conception.

As the ultimate goal of any IVF cycle is a healthy pregnancy, technologies that stand to improve IVF success rates, such as Natera’s All Chromosome Aneuploidy Screening test, hold great promise for couples facing infertility.

For more information on the PGD program at HRC Rancho Cucamonga, please contact us via our online form or call us at (909) 941-1120.