During the last thirty years preimplantation genetic testing has found diverse clinical application, expanding beyond the relatively small population of patients at high-risk of inherited disease transmission for whom it was initially intended. While the use of PGT has been highly successful in helping couples carrying gene mutations to reduce the incidence of affected pregnancies, it is now more commonly used for assessing chromosomal status of embryos generated during the course of routine IVF treatment. Chromosome abnormalities are extremely common in human IVF embryos and, in theory, the identification and preferential transfer to the uterus of euploid embryos should improve IVF treatment outcomes. Today, it is estimated that more than a third of all IVF cycles carried out in the United States utilise this type of testing to assist the selection of embryos, dwarfing the utilisation of PGT for other purposes. Recent technical developments suggest that PGT will provide patients with increasingly valuable reproductive strategies, while its growing capabilities may also pose ethical questions.

The main aim of preimplantation genetic testing (PGT), which up until recently was known as preimplantation genetic diagnosis (PGD), is the identification of embryos that are free of inherited genetic conditions. PGT can therefore be considered as a treatment option for couples where one or both partners are at risk of transmitting such a condition to their offspring. Inherited genetic conditions can affect gene function or chromosome structure, and could either be present in families or arise de novo. PGT for inherited mutations affecting gene function is defined as PGT for monogenic disorders or PGT-M, whereas PGT for inherited chromosome rearrangements is termed as PGT for structural rearrangements or PGT-SR (). The selection and preferential transfer of healthy embryos could lead to the birth of babies who are free of the genetic disorder for which PGT was carried out, as well as potentially eradicate it from the family. Hence, PGT can be considered as an alternative form of prenatal diagnosis, with the added advantage that it avoids the termination of affected pregnancies.