PGD is a procedure performed on embryos prior to their transfer to the uterus. To perform this technique, the embryos must develop to the blastocyst stage and then the blastocysts undergo biopsy where some cells are extracted from their trophectoderm for genetic analysis. After evaluation of the cells, embryos which do not present any genetic or chromosomal abnormality are transferred to the uterus. The inviable embryos are discarded.

PGD is appropriate in the following cases:

• One or both partners are carriers of a hereditary genetic disease.
• One or both partners are carriers of a genetic condition. For example, translocations (chromosomal abnormalities), inversions (of chromosomes), etc.
• Repeated failure of conventional in vitro fertilization or ICSI.
• Repeated miscarriages.
• Altered FISH test results in spermatozoids.