Preimplantation Genetic Testing: PGD and PGS

Preimplantation genetic testing is a cutting-edge procedure performed in conjunction with in vitro fertilization in which minute amounts of DNA are extracted from the embryo. By analyzing this DNA, our physicians can select embryos that may be free of a specific genetic disease or any chromosomal abnormalities. The Fertility and Reproductive Medicine Center provides this service in partnership with Genesis Genetics and at times other reference labs

How it works

PGD/PGS requires in vitro fertilization and the creation of embryos, which are then grown and biopsied 3-6 days after the egg retrieval process.  Currrent data favors trophectoderm biopsy (embryos that are 5-6 days after retrieval) which requires the embryo(s) to be cryopreserved immediately after biopsy and transferred in a subsequent cycle after the ressults of the testing are available.

The trophectoderm cells ultimately develop into the placenta. The inner cell mass of cells that become the fetus are left alone.

trophbxTr

Trophectoderm biopsy being performed on blastocyst. Compared to biopsy at the cleavage stage, when only 1 or 2 cells (i.e blastomeres) are removed, trophectoderm biopsy allows the sampling of more cells/DNA.

Testing to avoid inheritance of a single gene disorder (PGD)

Many patients seek IVF to avoid the passage of an inherited disease to their offspring (cystic fibrosis, sickle cell disease). We work with you and your partner in conjunction with our reference lab partners to design a personlized DNA test in order to accurately diagnose which embryos are free of the inherited disease. The goal of this testing is to provide reassurance that your pregnancy will not be affected by the inherited disease.

HLA matching, for families with particular blood diseases, can also be implented to test embryos that might be a match for a family member/sibling – (so called “savior sibling”).

If you think PGD is right for you, then contact our office to schedule an appointment with one of our physicians.

Screening for chromosomal aneuploidy or translocations (PGS)

Preimplantation Genetic Screening (PGS) is another type of genetic testing but differs from PGD in that instead of testing for a specific genetic disorder, the embryo(s)’s chromosomes are being “screened” to see if there is an extra chromosome or a missing one.

Normally, competent embryos are slected based on their appearance, but this is not perfect. PGS can act as a tool to help us better select a competent embryo by selecting out the chromosomally abnormal (i.e aneuploid) embryos and only transferring the euploid (i.e normal) embryos. PGS has been used in multple settings to name a few:

  • recurrent pregnancy loss,
  • advanced maternal age
  • unexplained prior failed IVF

There remains debate regarding PGS and its application. It is critical that you talk to your physician to see if PGS is right for you.

It should be noted that PGS has been called different things but they are all describing the same thing. You may hear these terms used interchangeably.

  • PGS
  • PGD for aneuploidy screening (PGD-A)
  • Comphrehensive chromsomal screening (CCS)