PGS, or Preimplantation Genetic Screening, is a medical procedure used during in vitro fertilization (IVF) to assess the genetic health of embryos before they are implanted in the uterus. This screening helps identify any chromosomal abnormalities, increasing the chances of a successful pregnancy and reducing the risk of genetic disorders. The process involves taking a few cells from an embryo at the blastocyst stage and analyzing them for genetic information. PGS can be particularly beneficial for couples with a history of genetic conditions or those of advanced maternal age, as it helps ensure that only healthy embryos are selected for implantation.