Genetic Testing Before IVF
Fertility doctors perform genetic testing, also known as preimplantation genetic diagnosis (PGD), before in vitro fertilization (IVF) to select embryos that are free of chromosomal abnormalities and certain genetic disorders. The selection is necessary because some genetic conditions can cause embryo implantation or the pregnancy to fail. The child might also face physical, developmental or mental problems.
Such testing is not automatic, however. It is usually recommended when a woman's medical history or age might cause embryos to be affected by genetic disease. PGD is only possible using embryos resulting from eggs and sperm united in the laboratory.
For at-risk couples, PGD technology helps reduce the possibility of failed pregnancy by testing embryos before they're returned to the woman. Indications for the procedure include inherited genetic disorders, multiple miscarriages, the woman's advanced age, unexplained infertility and other unsuccessful IVF cycles.
For fertility doctors at Kansas City's Reproductive Resource Center, PGD is an important tool in increasing the chance of success in IVF. Being able to test embryos allows them to select only normal ones for the IVF procedure, reducing the possibility of miscarriage or birth defects.
PGD should be distinguished from other forms of testing, genetic or otherwise, before pregnancy. Tests are now available for an array of disorders, including cystic fibrosis, Down syndrome, thalassemia, Tay-Sachs and Canavan disease. These tests are performed on adults, not embryos, and are selected based on the person's family and personal history.
Cystic fibrosis causes mucus to clog airways in the lungs. A DNA test is used to find out if someone is a carrier. The disease affects approximately one in every 2,500 Caucasian babies. It has been recommended that all Caucasians who are thinking about getting pregnant ask their doctor about testing.
Down syndrome has often been linked to an extra chromosome and is a kind of mental retardation. A chromosome analysis performed on the blood of a family member with the disorder can help determine the type of chromosomal abnormality involved. A family history of Down syndrome or other mental retardation is an indication for testing.
Thalassemia results in anemia. Individuals with the disorder experience anemia and can have heart and liver problems. Testing is recommended for people of Asian or Mediterranean descent and consists of evaluating the size of red blood cells and hemoglobin.
Tay-Sachs victims usually die before they're seven years old. They lack a chemical that's necessary for proper brain function and experience retardation, blindness and seizures.
Canavan disease affects infants. The brain degenerates because the myelin sheath covering the nerve fibers fails to develop properly. DNA testing is recommended for people of eastern Ashkenazi descent.