After deciding to perform an in vitro fertilization, a lot of specialists recommend to perform a Preimplantation Genetic Screening (PGS), which allows selecting the embryo with the greatest chances of producing a pregnancy.

The PGS is generally performed on embryos prior to implantation, but it can be also done on oocytes prior to fertilisation. By this technique the number of chromosomes of an embryo is determined. Only those embryos with the correct number of chromosomes will be able to implant in the uterus and develop successfully into a healthy baby.

In order to perform this screening, a specialist extracts a few cells from a 5-day old embryo – which at this stage consists of hundreds of cells – extracts their DNA and assesses the number of chromosomes in each cell. Only those embryos with the right number of chromosomes will be transferred to the uterus increasing the chances of a successful pregnancy. Several recent studies show that by only selecting healthy embryos for implantation, more women will become pregnant and fewer will experience miscarriages.

The first study was hold in 1990 in England. Genetic analysis of embryos was initially used for special cases from families carrying an inherited genetic condition. Genetic screening of embryos is currently also used to improve in vitro fertilization results. Today more than 10,000 children have been born worldwide after PGS.