PGS is a technique used to assess embryos for chromosomal abnormalities. It involves the removal of one or more cells from embryos before they are transferred.
This is followed by testing of the cells to find out the number of chromosomes, using either NGS or array-CGH methods. If the cells are found to have an abnormal chromosome number, then the embryo is less likely to implant. In this way embryos can be screened in order to select the most viable embryos for embryo transfer.