Preimplantation genetic screening (PGS) for aneuploidy is a powerful genetic test that may be performed on embryos during IVF treatment to screen for numerical chromosomal abnormalities. PGS is performed on a small embryo biopsy prior to transfer and identifies which embryos are chromosomally normal. Chromosomally normal embryos are the most likely to develop to term and to be born as a healthy baby. PGS testing helps IVF physicians and patients decide which embryos to transfer.

PGS offers comprehensive analysis of all 24 chromosome types: the two sex chromosomes (X and Y) and the 22 other non-sex chromosomes. Normally there are 23 pairs of chromosomes in each human cell. A numerical change in the number of chromosomes is called aneuploidy. Aneuploidy is responsible for the vast majority of spontaneous miscarriages and can result in birth defects and mental retardation in live born babies. Most types of aneuploidy are not compatible with life. The most common syndromes caused by non-sex chromosome aneuploidies are Down syndrome, Edwards syndrome, and Patau syndrome. Aneuploidy is usually not inherited and can involve any chromosome; however, the likelihood of embryos being aneuploid increases with the age of the mother.