Preimplantation Genetic Screening

Research has determined that as women age, the likelihood of having an embryo with an abnormal chromosome increases, and conversely the chance of having an embryo with normal chromosomes decreases. It is theorized that with aging, chromosomes in eggs become less likely to divide correctly leading to extra chromosomes or chromosomes that are absent. Most embryos with chromosomal abnormalities fail to implant or if implantation occurs, the embryo fails in the first 12 weeks of pregnancy; however, some pregnancies will progress and the resulting child will be born with a genetic syndrome such as Downs’ Syndrome.

PGS allows for individuals and couples to achieve a healthy baby with additional information that may reduce the likelihood of miscarriage, decrease the risk of abnormal pregnancy, reduce the amount of time and additional costs inferred with multiple IVF cycles, and increase the likelihood of pregnancy with single embryo transfer (eSET).

There are many reasons PGS is performed. Some of the more common motives are:

  • Recurrent Miscarriages
  • Advanced Maternal Age (35 and older)
  • Previous IVF Failure
  • Single Embryo Transfer
  • Patient Concern
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Benefits of PGS Testing

Having PGS as a tool in your reproductive care can provide you and our staff with more information about your embryos and aids in minimizing the risk of transferring embryos with chromosome abnormalities. With the information gained from PGS testing, the number of embryos with incorrect number of chromosomes can be minimized before transfer to the uterus. Since the most common reason for miscarriage is chromosome abnormalities, by transferring genetically normal embryos, implantation rates substantially increase and miscarriage rates are decreased. In the end, having the chromosome status of each embryo increases the likelihood of achieving pregnancy through IVF.

As with any testing procedure, one of the most commonly asked questions is, “What information will I gain from this test?” Results are interpreted to recognize the following:

  • Chromosome Duplications- An extra copy of chromosomes can result in conditions such as Down Syndrome (Trisomy 21)
  • Chromosome Deletions – Missing copies of chromosomes
  • Sex-Chromosome Abnormalities- Duplications or deletions of X and Y can result in a multitude of conditions. Commonly known examples of these conditions include Klinefelter Syndrome and Turner Syndrome.
  • Gender Identification – The gender of an embryo can be identified through PGS.

PGS is only used to test for chromosomal abnormalities, while PGD is used to test for single gene mutations associated with genetically inherited diseases (ie Cystic Fibrosis, Huntington’s Disease, Muscular Dystrophy and many more.)

Steps Involved in PGS Testing

If you are considering PGS, then you may be curious as to what the PGS process involves. The initial steps take place at The Fertility Center of Oregon’s embryology Laboratory with transfer of biopsied cells submitted for genetic testing by an outside laboratory.

The steps involved in PGS are as follows:

  1. Normal IVF treatments occur at FCO, where eggs will be collected and fertilized.
  2. Embryos will develop for 5 days.
  3. On Day 3 of embryo development, hatching of the zona pelucida takes place (to assist in hatching of blastocyst on day 5.)
  4. Cells will be removed via a biopsy procedure by our Embryologist at FCO.
    • Previously hatched embryos will be hatching from zona pelucida.
    • Using a micro laser 4-5 cells of the trophectoderm (placental cells) are removed from the blastocyst.
    • Embryos are returned to growth dishes and biopsied cells are placed in a lysis solution to preserve genetic material (DNA).
  5. The biopsy is sent to Genesis Genetics in Phoenix, Arizona by a specialized courier to arrive the same day as the biopsy.
  6. Chromosomes are analyzed by expert scientists to evaluate duplications and/or deletions utilizing Next Generation Sequencing (NGS).
  7. The chromosomal findings are reported to FCO on the morning of the 6th day of embryo culture.
  8. Embryo transfer is completed on Day 6 of embryo growth or embryos are frozen and transferred at a later date.