Pre-implantation Genetic Testing (PGT)
Preimplantation Genetic Testing (PGT for short) is a diagnostic procedure for assessing the genome of a created embryo for abnormalities, while keeping it intact and available for transfer and implantation. Based on the type of genetic analysis conducted, defined by the analysis target, there are different types of testing:
Preimplantation Genetic Testing for Aneuploidy (PGT-A)
This diagnostic method screens the embryo for chromosomal abnormalities, via assessing the number and structure of the embryo’s chromosomes. It is the most frequently utilized type of PGT and it allows for the selection of euploid embryos only, meaning those that have normal chromosomes, via next generation sequencing (NGS) methods.
Transfer of tested, euploid embryos has been shown to increase the implantation, ongoing pregnancy and birth rates per embryo transfer, while also reducing miscarriage rates, thus improving the odds of success with fewer attempts.
Preimplantation Genetic testing for Monogenic defects (PGT-M)
Previously refered to as Preimplantation Genetic Diagnosis (PGD), this type of testing is not as frequent as PGT-A and has more specific indications. Namely, PGT-M checks for specific mutations in individual genes of the embryo, which may cause a number of genetic conditions, for example cystic fibrosis, muscular dystrophy, Huntington disease, and many others.
This test is only recommended if the parents have the condition or are carriers of the condition and is not performed as a routine.
Application of PGT-A and PGT-M in Greece is regulated by the Greek National Authority of Assisted Reproduction and requires specific prerequisites, along with issuance of an official licence by the Authority for each case. Preimplantation Genetic Diagnosis use for gender selection of the embryo is illegal in Greece.