If your clinic has brought up testing your embryos, you have probably met three acronyms that look almost identical on the page: PGT-A, PGT-M, and PGT-SR. They share a name, they happen at the same moment in your cycle, and they all start with the same biopsy.
What they tell you could not be more different. One counts chromosomes. One looks for a specific inherited condition your family already knows about. One sorts out a rearrangement in how your chromosomes are arranged.
This guide covers what each test actually screens for, how the biopsy and freeze-all process works, what your results mean, and what the evidence says about whether testing improves your odds.
"PGT changes what you know about your embryos. It does not change your embryos."
The short version
Genetic testing, by the numbers
What it is
A sorting tool, not a treatment
Preimplantation genetic testing is performed on embryos created through IVF, before any of them are transferred. A few cells are removed from each blastocyst, sent to a genetics lab, and analyzed. You get a report on each embryo, and you and your care team decide what to transfer and in what order.
The most useful thing to understand up front is that PGT does not repair anything, improve anything, or make a struggling embryo stronger. If a cycle produces three blastocysts, testing does not turn them into better blastocysts. It tells you more about those three. Everything else about embryo quality is decided before the biopsy, which is why embryo grading and genetic testing answer separate questions.
All three versions require the same infrastructure: a full retrieval cycle, embryos cultured to blastocyst, a biopsy, and in nearly every case a freeze while results process. That is why testing is a cycle-level decision rather than something added at the last minute.
The three tests
PGT-A, PGT-M, and PGT-SR
PGT-M and PGT-SR are almost always run alongside PGT-A on the same biopsy, since knowing an embryo is unaffected by a genetic condition tells you nothing about its chromosome count. And both are targeted: PGT-M looks only for the variant it was designed to find, and is not a broad genetic health check.
Families use PGT-M for conditions including cystic fibrosis, sickle cell disease, spinal muscular atrophy, Tay-Sachs, Huntington disease, and fragile X, along with predisposition genes such as BRCA1 and BRCA2. PGT-SR applies when a parent carries a balanced translocation, a Robertsonian translocation, or an inversion. Carriers are typically healthy and often have no idea until repeated miscarriage prompts a karyotype.
What the research says
The honest case for PGT-A
Aneuploidy means the wrong number of chromosomes. Most aneuploid embryos either fail to implant or end in early miscarriage, and aneuploidy rates climb steadily with the age of the eggs. That is the biological reason IVF success rates fall with age even when everything else looks fine, and it is the case PGT-A rests on.
That finding surprises most patients, and it deserves an explanation rather than a shrug. The reason comes down to two different questions. Does PGT-A improve your odds on any single transfer? Often yes, because you skip embryos that were never going to work. Does it improve your odds of eventually having a baby from that retrieval? For most patients the trials say no, because those same embryos would have failed on their own and you would have moved to the next one.
So the honest case for PGT-A is about the shape of the journey rather than the destination: fewer transfers that end in disappointment, fewer early losses, less time spent on embryos with no potential. For many patients that is worth a great deal. A post hoc analysis of the STAR trial did suggest a per-transfer benefit for patients between 35 and 40, which is where most clinics focus the conversation.
The process
How a testing cycle actually runs
Your results
What the report categories mean
| Result | What it means and what usually happens next |
|---|---|
| Euploid | The expected number of chromosomes. These are transferred first. Live birth after a single euploid transfer is generally better than half, and holds up reasonably well across age groups, but it has never been a guarantee. |
| Aneuploid | A whole extra or missing chromosome. These are not usually transferred, and the decision here is typically straightforward. |
| Mosaic | The sample contained a mix of normal and abnormal cells. The science here has shifted considerably. Mosaic embryos have been transferred and have produced healthy babies, at somewhat lower rates than euploid. This is a reason to speak with a genetic counselor, not a verdict. |
| No result | A small share of samples fail to amplify or return an inconclusive read. Depending on your clinic, the embryo may be able to be thawed and rebiopsied. |
One category causes more distress than the rest. If a mosaic result lands in your inbox on a Friday afternoon, the right move is to wait for the counseling appointment rather than reading forum threads over the weekend. Rushing that decision is something patients tell us they regret.
Common questions
What patients ask us most
PGT screens for one specific thing at a time. It does not evaluate the vast majority of genetic conditions, and it says nothing about birth defects that are not chromosomal. A euploid result means the chromosome count looked right in a handful of cells from a five day old embryo.
Standard prenatal screening and diagnostic testing during pregnancy remain the recommendation regardless of what your embryo report said. PGT is a screening test, not a diagnosis.
PGT-A analyzes all chromosomes including X and Y, so the information is generated as part of the test. Whether your clinic discloses it, and whether it can be used in choosing which embryo to transfer, depends on clinic policy and in some countries on the law. Ask before your cycle rather than after results arrive.
This is a genuinely hard day, and it does not mean you cannot have a child. The result reflects the chromosomal quality of one cohort of eggs at one moment in time, and outcomes often differ from cycle to cycle. Your clinic may suggest protocol changes, another retrieval, or a wider conversation about options.
The emotional weight of this result is real and worth taking seriously. Prima partners with Alma to connect patients with therapists who specialize in fertility.
Previously frozen blastocysts can usually be thawed, biopsied, and refrozen. That does mean an additional freeze and thaw cycle for those embryos, so it is worth discussing with your embryology team whether the added information justifies the added handling in your specific situation.
PGT-M for a documented family condition is more often covered than PGT-A used as a general screen, but this varies widely by plan. Billing is frequently split between your clinic and an outside genetics lab, so ask both for written estimates rather than assuming one covers the whole thing.
For the medication side of a testing cycle, you can request a free price quote before you start, and our financing guide covers the savings programs that apply.
What is your lab's blastocyst rate and biopsy experience? How do you report and counsel on mosaic results? What happens if an embryo returns no result, and is rebiopsy available? What is the full cost including biopsy, lab fees, and probe development if PGT-M applies?
And the one that matters most: given my age and my expected embryo number, what do you expect testing to change for me specifically? A good answer will be concrete rather than general.
Where Prima fits in
Two medication phases, separated by a wait
Genetic testing decisions belong to you, your reproductive endocrinologist, and ideally a genetic counselor. What we handle is everything around them.
A PGT cycle splits your medications into two phases: stimulation for the retrieval, then a frozen transfer protocol running on estrogen and progesterone for weeks afterward. Those phases are often separated by a month or more while results process and your clinic schedules the transfer. That gap is exactly where a refill quietly falls through, because the urgency of retrieval has passed.
Prima keeps your protocol on file across both phases, ships cold-chain medications to arrive when you need them. Same-day delivery in New York City, next-day nationwide, Monday through Saturday.
Testing is a highly personal choice, and there is no answer that is right for everyone. Ask what each test would tell you, what it would not, and what your clinic expects it to change in your case. Those three answers are usually enough to decide.
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Clinical Note
Guidance in this post reflects the American Society for Reproductive Medicine Practice Committee opinion on preimplantation genetic testing for aneuploidy (2024), published outcome data on mosaic embryo transfer, and current clinical practice on trophectoderm biopsy and vitrification. Testing protocols, reporting categories, and disclosure policies vary between clinics and genetics laboratories. This content is educational and does not constitute medical advice. Decisions about genetic testing should be made with your reproductive endocrinologist and, where appropriate, a certified genetic counselor.
