PREIMPLANTATION GENETIC DIAGNOSIS (PGD)

Preimplantation genetic diagnosis (PGD)

Preimplantation genetic diagnosis (PGD) is a laboratory procedure carried out before embryo transfer in order to identify inherited genetic diseases in the embryo. In this way we can detect gene mutations associated with specific conditions before embryo transfer and implantation, thereby preventing disease before the pregnancy begins and, by extension, enabling the birth of healthy children. Specific gene mutations responsible for known congenital and hereditary diseases in the embryo are looked for (using PCR). The technique can be applied at the stage of the unfertilised mature egg (first polar body biopsy), the day-3 embryo (blastomere biopsy) or the blastocyst (trophectoderm biopsy).

PGD is indicated for

• Couples who carry a single-gene or sex-linked disease.
• Couples who wish to have a tissue-matched baby who can be a bone marrow donor for another sick child in the family.

Examples of diseases for which preimplantation genetic diagnosis is used are beta-thalassaemia, cystic fibrosis and others. With the continuing progress of genetics, more genes responsible for specific hereditary diseases are expected to be identified, making it possible to prevent more diseases, even forms of cancer.

Preimplantation genetic diagnosis has an advantage over conventional methods of prenatal testing, namely amniocentesis and chorionic villus sampling, because it avoids the possibility of terminating the pregnancy if testing is positive for the specific condition in the fetus. Finally, it must be made clear that the method looks for specific diseases and does not rule out the birth of a child with a different kind of genetic defect.