What is PGS (pre-implantation genetic screening)?
Preimplantation genetic screening is a method used to check the number of chromosomes in an embryo. Up to 50% of embryos produced may have an incorrect number of chromosomes described as aneuploidy. This is a common cause of miscarriage and implantation failure. PGS can also be used to test for genetic conditions that are caused by an abnormal number of chromosomes. These include Downs syndrome and Turner syndrome.
The patient undergoes a specialized IVF process using ICSI to create a number of embryos. After three to five days, one or more cells are taken from each embryo. These cells can then be tested to determine the number of chromosomes present. The embryos are frozen to allow time for the genetic testing to take place.When the results are confirmed, the embryologist selects the embryo with the correct number of chromosomes to transfer back to the patient.
Who can benefit from Pre-implantation Genetic Screening?
PGS is offered to women over the age of 37. Using PGS, the chances of pregnancy from embryo transfer in older women are as good as those seen in younger women. However, with advanced maternal age, the chances of making an embryo with the correct number of chromosomes are lower. PGS may also be offered if you or your partner have a history of chromosomal abnormality-related conditions in your family. It is important to note that PGS cannot be used to detect the presence of conditions caused by single mutations in genes; for these cases, preimplantation genetic diagnosis (PGD) can be used.
PGS is one of the investigations recommended if you have had a recurrent miscarriage or previous failed IVF.
What are the benefits of PGS?
A significant benefit of PGS is the reduction of miscarriage rates. Aneuploidy is a large contributor to recurrent miscarriage, so by testing embryos before transfer, the rate of miscarriages are reduced and can be of great help to the couples struggling with these issues.