Preimplantation Genetic Testing

PGT! PGT-A, PGT-SR, PGT-M! WTF does it all mean? Well hell if I know, I mean, these are questions for your doctor, right? Well, probably better to discuss with a genetic counselor if your clinic has one on staff. BUT, I’ll try to give you a reaaallly basic breakdown.

Who needs genetic testing? As an embryologist, what I most commonly see is that patients in their 20s are not doing PGT unless they have a specific medical history where testing would be indicated. Patients around 32 and older typically opt in to testing. Some insurance carriers don’t cover this, some do, some cover a certain number, and some only want to use certain companies for testing. I’ve seen prices anywhere from $350 per embryo to $800 per embryo. The reason why patients in their 30s and 40s are testing more than patients in their 20s comes down to likelihood of abnormal results.

PGT-A stands for “Preimplantation Genetic Testing for Aneuploidy” which means the embryo is being tested for the correct number of chromosomes. When an embryo comes back as aneuploid, this means it has an abnormal number of chromosomes. When an embryo is determined to be euploid, it has the correct and expected number of chromosomes for a human.

PGT-SR stands for PGT with testing for Structural Rearrangement. These means the embryo is tested for any rearrangements you may have learned about in basic genetics classes such as translocations, duplications, deletions, etc… This may be suggested to patients with medical and/or familial histories that would indicate this as an appropriate test.

PGT-M is PGT for Monogenic diseases. This test investigates specific and often uncommon diseases that have been established to exist in the patient’s genetic history either as being affected by the condition or a carrier for the condition.

PGT-M and PGT-SR will always include the basic PGT-A information in their reports as well. Some reports may include degrees of mosaicism as well, which in basic terms means some cells are normal, some are abnormal.

What do patients and providers do with this information? Once an embryo has been established as euploid, it is considered a candidate for embryo transfer. If an embryo has gone additional testing, it will depend on the specific information returned, however even if an embryo does not exhibit structural rearrangement or carrier status for a monogenic disease, if it’s aneuploid, it will NOT be considered for transfer.

Why not transfer aneuploid embryos? This is a controversial topic! Some folks will advocate for saving and even potentially transferring affected embryos based on a concept that it’s possible for blastocysts to have the ability to “self correct” the ploidy of the embryo by rejecting the abnormal cells and integrating only the normal cells into the developing embryo. It is however by far the rule that clinics will not transfer aneuploid embryos. For other results, for example a euploid embryo that is a carrier for a monogenic disease, it would typically require genetic counseling and acknowledgement in writing that the embryo is affected.

Clinics refusing to transfer aneuploid embryos is not done to be punitive or cruel, though it may feel that way. It is done because current science and research shows that aneuploid embryos result in miscarriage. By eliminating aneuploid embryos from the potential pool of embryos to be transferred, the likelihood of miscarriage is reduced.

Hopefully this clarifies some of the basic questions you may have about PGT, but as always, please default to your primary, REI, and genetic counselors for the most up to date and appropriate information as it specifically applies to you! The more information you have, the more confidently you can drive forward with your family building plan!

for your bros.