40 years ago, the field of reproductive medicine saw its first successful birth from in vitro fertilization (IVF) and since then, technological advancements have led to the births of over 8 million more IVF babies. Included in these advancements was the development of Preimplantation Genetic Testing (PGT), which was designed to help improve the chances of a successful IVF cycle (and consequently, a healthy baby!), which now benefits thousands of families each year.
Currently, PGT falls into two categories: Preimplantation Genetic Screening (PGS) and Preimplantation Genetic Diagnosis (PGD). However, within the past few months, leading professional medical societies focused on reproductive health (including ICMART, ASRM, and ESHRE) have come together to announce new names for PGS and PGD with the goal of more accurately representing these tests and driving standardization in terminology across the globe.
Take a look at these changes below:
By the end of 2018, PGS and PGD will be replaced with this new nomenclature that better aligns with the continued growth of the field of reproductive genetics.
So what do these changes mean for patients?
PGS → PGT-A
PGS is designed to assess whether embryos have the correct amount of genetic material. Genetic material is housed within structures called chromosomes, and when chromosomes are missing or extra, it can lead to improper development and functioning. Embryos with the incorrect amount of genetic material, known as aneuploid embryos, typically fail to implant, which result in a miscarriage or lead to the birth of a child with a genetic disorder. Conversely, embryos with the correct amount of genetic material, known as euploid embryos, have a better chance of resulting in a successful pregnancy.
Because PGS looks for aneuploidies, it has been renamed as Preimplantation Genetic Testing for Aneuploidies (PGT-A).
PGD → PGT-M and PGT-SR
While PGS (PGT-A) looks for missing or extra chromosomes, testing that is currently known as Preimplantation Genetic Diagnosis, or PGD, looks for specific inherited abnormalities, and can be performed either for inherited genetic diseases or for inherited chromosome rearrangements. The new terminology for PGD will better differentiate between these two distinct types of PGD, which are appropriate for different patient populations and are run on different technology platforms.
Preimplantation Genetic Testing for Monogenic/Single-Gene Disorders (PGT-M) looks for specific inherited conditions controlled by a single gene, like Huntington’s disease, sickle-cell disease, or Fragile X syndrome.
Preimplantation Genetic Testing for Chromosomal Structural Rearrangements (PGT-SR) looks for specific inherited chromosome abnormalities, like reciprocal translocations, Robertsonian translocations, or inversions.
What does this mean for you?
In the coming months, we will be implementing these nomenclature changes across our website, social media, and formal documents, such as order forms and reports. We are hopeful that the changes in PGT nomenclature will allow patients and professionals to better differentiate between the various types of preimplantation genetic testing, providing much-needed clarification in such a complex field.