We apply PGS when we wish to prevent mutated genes from being passed on to the child by parents who have been affected or are carriers of genetic diseases. For instance, if both parents are carriers of the thalassemia gene, with PGD the affected embryos can be identified prior to embryo transfer.
In which cases do we apply pre-implantation genetic screening techniques (PGS)?
We apply PGS when there is a strong possibility of having an increased number of embryos with chromosome abnormalities. For example, it has been found that for women of older reproductive age, there is an increased rate of chromosome abnormalities in their oocytes.
Embryo screening before transfer can increase the chances of implantation or, if no normal embryo is found, prevent the transfer of embryos that cannot lead to pregnancy.
Additionally why apply PGS when implantation fails after multiple IVF attempts. In this case, pre-implantation genetic screening can increase the likelihood of conception or explain the causes of failure.
Finally when we wish to decrease the number of embryos which will be transferred to the uterus to avoid multiple pregnancy. In this case, pre-implantation genetic screening can detect the embryos with the highest implantation potential, so that we can achieve good pregnancy rates even by transferring a single embryo.