The difference between PGS and PGD
Hopeful parents who are concerned about passing along genetic diseases to their children have more options today than ever before. Preimplantation genetic screening, PGS, and preimplantation genetic diagnosis, PGD, are add-on services at the end of an IVF cycle. Both types of genetic embryo testing allow our Newport Beach fertility center to ensure that only genetically normal embryos are transferred, increasing the chance of a successful pregnancy and a healthy baby. However, the procedures used and the goal of testing are different for PGS and PGD.
Who needs PGS and PGD?
The first thing to understand about PGS and PGD is that PGS essentially counts chromosomes, while PGD goes a level deeper to examine genes for specific abnormalities.
Both types of testing employ the same embryo biopsy technique, which involves making a tiny cut in the outer shell of each IVF embryo. Once the opening is made, a few cells are removed and sent to a specialized genetics lab for testing, while the embryos are frozen and the hopeful parents wait for results.
- With PGS, geneticists examine the chromosomes of each embryo, verifying that 46 chromosomes – 23 pairs – are present. If more or fewer chromosomes can be seen, the embryo is genetically abnormal and disqualified for uterine transfer.
- With PGD, geneticists don’t just count the chromosomes. They actually deconstruct specific strands of DNA and test them for known genetic diseases that run in the hopeful parents’ families, such as cystic fibrosis, Tay-Sachs disease, hemophilia, sickle cell disease and spinal muscular atrophy. If those specific genetic defects are identified, that embryo will not be transferred.
Because PGS is looking for general chromosomal abnormalities, it’s an excellent choice for hopeful parents concerned about genetic issues related to advanced maternal age, such as Down syndrome, as well as for people who have experienced recurrent miscarriage or failed IVF cycles.
For individuals or couples who have or carry a specific genetic disease, or who are simply concerned about a family history of genetic disorders, PGD takes PGS to the next level. Geneticists can already test for more than 1,000 specific genetic disorders, and that number keeps expanding as genetic research continues to unlock the mysteries of human DNA.
Many people are unaware that they may carry genetic diseases, as they could be symptomless carriers. For this reason, we encourage all men and women who come to us for fertility care to take advantage of genetic screening. If genetic testing reveals any genetic abnormalities, PGD will allow our genetics lab to look for the gene tied to that specific disorder in the embryos, so that hopeful parents can be confident that their children will not become carriers or develop that disease.
Break the chain of heritable disease
Both PGS and PGD give hopeful parents confidence that they are doing everything possible to increase their chances of having a successful pregnancy and healthy baby.
If you have concerns about heritable illness in your or your partner’s family, advanced genetic testing makes it possible for you to break the chain of heritable disease. To learn more about PGS and PGD, contact us to schedule a consultation at our Newport Beach fertility center.