Preimplantation Genetic Diagnosis/Screening (PGD/PGS)

Preimplantation genetic diagnosis (PGD) involves the genetic testing of embryos followed by the selective transfer of genetically normal embryos.

PGD has also currently expanded to perform aneuploidy screening (preimplantation genetic screening – PGS). PGS is offered to couples with a high risk for a child with a genetic defect such as cases of advanced maternal age, repeated IVF failure, repeated miscarriage and non-obstructive azoospermia.

PGD/PGS can be offered for several genetic diseases and syndromes. Common genetic diseases that can be prevented through PGD/PGS include any chromosomal abnormalities (e.g. Down syndrome), thalassaemia, cystic fibrosis, fragile X syndrome, X-Linked disorders, e.t.c. In Cyprus, where the frequency of the individuals that carry the gene of b-thalassaemia is high in the population, PGD is of great importance.

PGD involves the removal of cells from the trophectoderm of a day 5 blastocyst, with the aid of a laser. A small hole is opened on the zona surrounding the blastocyst, through which a small number of cells are removed to be sent for analysis. 

 Blastocyst biopsy is only performed on high quality blastocysts that have had the opportunity to self-correct and undertaken the first cellular differentiation. Blastocyst screening however, is coupled to cryopreservation as it requires freezing of the blastocysts in order to allow for the results of the analysis to become available.