Understanding PGS and PGD
Women undergoing in vitro fertilization (IVF) now have more options than ever before to ensure the health of a future baby. Preimplantation genetic screening (PGS) and preimplantation genetic diagnosis (PGD) are add-on services during IVF. Both tests can help ensure that the best embryo is selected for transfer, increasing pregnancy success rates. What are the main differences between these preimplantation tests?
The PGS approach
Preimplantation genetic screening is available to any patient who wants to learn more about chromosomal abnormalities in the embryos retrieved. To perform the PGS test, a few cells are removed from the early embryo and sent to the lab to be analyzed. Typically, a baby should have 46 chromosomes, but if there is one more or one less, a chromosomal abnormality is said to have occurred. The most common chromosomal abnormality is Down syndrome. If the PGS test results show a problem with the chromosomes, the patient can choose not to transfer that specific embryo. Instead, a chromosomally normal embryo can be selected, increasing the chance of a successful pregnancy.
Learning more with PGD
Preimplantation genetic diagnosis is typically reserved for couples with a known genetic disease or chromosome abnormality that could be passed down to the baby. This test is done the same way as PGS, taking a few cells from the early embryo. However, PGD looks for more than just chromosomal abnormalities. The more advanced screening test can also look for chromosomal translocations. Screening for single-gene defects such as cystic fibrosis, sickle cell anemia, and muscular dystrophy is another popular reason to have PGD done.
Generally speaking, PGS can be requested by anyone undergoing IVF to learn more about the health of the embryo before transfer. Women over 35, who are at higher risk of chromosomal abnormalities, may benefit the most. The PGS test can also be used by couples who want to select a specific gender. The PGD approach is reserved for patients at risk of passing a genetic disease or chromosome problem to offspring. Before having either test done, patients should meet with a genetic counselor to understand the pros and cons of each approach.
Are PGS and PGD safe?
Preimplantation genetic screening and diagnosis are commonly done during the IVF process. By taking just a few cells from the early embryo, a plethora of information can be obtained without harming the development of the future baby. Since the testing takes place on the embryo after retrieval, there are no risks to the mom.
An informed decision
PGS and PGD are great options for couples who want to learn more about the health of the embryo before transfer. By screening for genetic abnormalities, translocations, and single-gene defects ahead of time, the fertility clinic can select the best embryo for use during IVF. Early screening can increase the success rate of IVF and is an option worth considering.