What’s the Difference Between PGD and PGS?

Genetic testing as part of IVF often ensures the greatest possibility for a successful clinical pregnancy. PGS (preimplantation genetic screening) and PGD (preimplantation genetic diagnosis) are often mentioned in conjunction with treatment, but what’s the difference between them?

Dr. Desiree McCarthy-Keith (Georgia Reproductive Specialists), an IVFAdvantage specialist, explains the differences between PGD and PGS and when they are most beneficial.

“Preimplantation genetic diagnosis (PGD) is a technique used to determine if an embryo carries a specific gene mutation before a pregnancy occurs,” Dr. McCarthy-Keith says. “Preimplantation genetic screening (PGS) allows for screening of embryos for chromosomal abnormalities.” So PGD screens for specific diseases that the embryo could be a carrier of, and PGS is used to determine if an embryo has the proper amount of chromosomes to allow for a proper implantation.

“Many diseases, such as sickle cell anemia, cystic fibrosis, and Tay-Sachs, are caused by a specific gene mutation,” Dr. McCarthy-Keith says. This is where PGD comes in to determine which embryos are carriers for such diseases and which are not.

Chromosome abnormalities, on the other hand, can lead to early pregnancy loss or failed implantation. PGS allows the embryos to be screened to determine which are structurally normal and give the best chance for proper implantation. According to Dr. McCarthy-Keith patients with a higher chance of chromosomally abnormal embryos include women of advanced age, women who have had recurrent miscarriage, those with repeated failed IVF cycles, and couples with severe male factor infertility.

PGD or PGS take place after the eggs are retrieved and fertilized with sperm in the laboratory. A cell biopsy is then taken from the embryo and then chromosome and genetic analysis is performed. “If genetically or chromosomally normal embryos are selected for transfer,” Dr. McCarthy-Keith says, “the risk of conceiving a child affected with a known genetic disease is reduced and chance for a successful pregnancy may be increased. Prenatal diagnostic testing can be used to confirm PGD/PGS results once a pregnancy is underway.”

Got questions about fertility treatment, IVF, or financing? We’re here to simplify the process for you: (646)-350-0748