Preimplantation genetic diagnosis (PGD) may help patients have a successful pregnancy and a child free from selected genetic disorders. Embryos are tested for genetic disorders before pregnancy has started. Embryos are obtained by combining eggs and sperm in the laboratory (in vitro fertilization). From each embryo, one or two cells are removed and tested. If an embryo is judged to be free of the tested disorder, it may be transferred to the uterus.
Patients whose children are at increased risk for a specific genetic disorder may benefit from PGD. Some may have affected family members, or a family ancestry that puts them at risk for transmitting a particular disorder to their offspring.
Preimplantation diagnosis has been used to test for the following:
- X-linked disorders such as hemophilia and Duchenne muscular dystrophy
- Single-gene disorders affecting either males or females, such as cystic fibrosis
- Structural chromosomal abnormalities, such as translocations
- Abnormal chromosomal numbers (aneuploidy), such as Down syndrome
The Emory Reproductive Center does offer PGD for aneuploidy screening. We recommend aneuploidy screening for selected patients with advanced maternal age, recurrent pregnancy loss and prior aneuploidic pregnancy.
At the Emory Reproductive Center, ethical guidelines have been established for PGD. These guidelines include the decision not to offer gender determination for social reasons (also known as family gender balancing).
PGD begins with the same process as in vitro fertilization, with fertility medications, egg retrieval, and insemination. The fertilized eggs will be allowed to develop for one or more days under controlled laboratory conditions. When the embryo reaches a certain stage in development, one or two cells are removed from each embryo for PGD testing and the embryos are returned to the culture medium. Studies have shown that cells can be removed at this stage without affecting the normal development of the embryo. The individual cells are tested using procedures such as polymerase chain reaction (PCR) or Fluorescent In-Situ Hybridization (FISH), each of which is sensitive enough to detect abnormalities in a single cell. When all the test results are gathered, a decision will be made as to which of the unaffected embryos, if any, are most suitable for transfer to the uterus.
If you become pregnant following embryo transfer, we would like to remain in contact with you for the duration of your pregnancy. Although diagnostic accuracy is very high, the demands of PGD are such that the results can never be 100 percent guaranteed. For this reason, you are encouraged to consider prenatal testing (amniocentesis or chorionic villus sampling) to confirm the PGD result.