Preimplantation Genetic Diagnosis
Preimplantation genetic diagnosis (PGD) was first used in 1989 and resulted in the birth of a normal female baby that was free of the specific genetic disease that was carried by the parents. Since then, many children have been born after PGD. Each year, the number of genetic conditions that can be analyzed by the PGD lab grows. PGD is done when a couple is concerned about passing on a specific disease or condition to their children and there is a specific gene marker or group of markers to identify the condition in the embryo. PGD is designed to help detect genetic abnormalities in embryos before implantation, thereby avoiding the transfer of affected embryos.
Examples of couples who may use PGD are those who carry genes for:
- Robertsonian and reciprocal translocations
- Fanconi’s anemia
- Sickle cell anemia
- Tay-Sach’s disease
- Cystic fibrosis
- Myotonic dystrophy
- Many many others
PGD involves the use of IVF to create the embryos. Each embryo then has cells removed from them in the lab and then analyzed for the genetic problem in question. Once the results of the PGD analysis are known, the embryos that are free of the genetic problem are chosen for embryo transfer.
Preimplantation Genetic Screening
Preimplantation genetic screening (PGS) is an evolving technology that is being used increasingly as part of the IVF process for couples. It involves the chromosomal analysis of the embryos generated during the IVF cycle. This way embryos that are put back into the uterus are known to be chromosomally normal. This is felt to increase pregnancy rates and reduce miscarriage rates. Many embryos that are generated in an IVF cycle are chromosomally abnormal and if put into the uterus, will either not implant (resulting in a negative pregnancy test) or if they do implant, result in an early miscarriage. All women of all ages make some chromosomally abnormal embryos because the abnormality arises from the eggs used. All women have some abnormal eggs in their ovaries no matter what their age is. PGS is currently the only method available to determine “embryo quality”.