Pre-implantation genetic diagnosis (PGD) is a technique that allows the testing of embryos for genetic disorders prior to performing their transfer back into the uterus. These genetic conditions can interfere with embryo development and implantation into the uterus, resulting in pregnancy loss or the birth of a child with physical problems, developmental delay or mental retardation. In addition, the PGD technique is extremely helpful for patients whose child may be at high risk of inheriting a genetic disease.
The indications for PGD include: advanced maternal age, recurrent miscarriages, previous unsuccessful IVF cycles, unexplained infertility, male factor infertility and a familial history of an inherited genetic disorder. Thus, the PGD technology improves the chances of a successful pregnancy and birth of a healthy child for couples with any of the previously mentioned diagnoses.
PGD can only be performed as a part of an IVF cycle. IVF is necessary to have access to the embryos and to determine which embryos are free of disease in the embryology laboratory. After the couple completes an IVF cycle, the embryos undergo a biopsy in which one or two cells from each resultant viable embryo are tested for DNA changes (mutations) responsible for a particular condition. It is currently possible to test for over 100 genetic diseases, including but not limited to Down syndrome, cystic fibrosis, sickle cell anemia, thalassemia, Tay Sachs disease, Huntington’s disease, Duchenne/Becker’s muscular dystrophy, myotonic dystrophy, spinal muscular atrophy, hemophilia and some types of leukemia. At the time of DNA testing, the presence of the sex chromosomes (X and Y) could also be determined, allowing the determination of the gender (sex) of the embryo.