Preimplantation genetic screening (PGS) is performed to identify de novo aneuploidy in couples presumed to be chromosomally normal to allow selection of those embryos with a normal karyotype. PGS with cleavage stage embryos and FISH decreases chances of live birth. Major clinic utility is to reduce multiples without reducing delivery rates allowing SET with high success. However, consider no PGS with single embryo transfer (SET) followed by SET/FET if not successful, is as success is the same. The value of PGS to select best embryos for transfer in couples with no known chromosomal or genetic abnormality. There is no high quality evidence that PGS improves cumulative live birth rates in these couples, including those with advanced maternal age (AMA), recurrent in vitro fertilization (IVF) implantation failure (RIF) and recurrent pregnancy loss (RPL). Among those with RPL, PGS will reduce the risk of subsequent loss but not increase the chances of having a live born baby.