Preimplantation genetic diagnosis (PGD) for single gene disorders is a powerful genetic test that may be performed during IVF treatment to screen embryos that are at risk to develop a serious genetic disorder. PGD is performed on a small embryo biopsy and identifies which embryos are not at increased risk of developing the disease. The goal of PGD testing is to help couples build a healthy family. PGD is done before the pregnancy is established and helps avoid difficult decisions and situations.
Our DNA is organized into small segments called genes. There are about 25,000 genes in humans, all of which influence our growth and development. Just like chromosomes come in pairs, most genes also come in pairs, one copy inherited from the egg and the other from the sperm. When the function of a gene is altered by a change (called a mutation) in the DNA sequence, a genetic disease can result. These mutations can be transmitted in families from generation to generation, or can be a new change in an individual (de novo).
Common examples of conditions caused by mutations in single genes (monogenic disorders) include spinal muscular atrophy (SMA), cystic fibrosis, and Fragile X disease. During the IVF process, PGD can be used to screen embryos for these conditions. Embryos that are not at increased risk for developing the single gene disorder are identified and preferentially transferred for the pregnancy. The goal of PGD testing is to help couples build healthy families.