When couples go through IVF, there is often a point where the doctor brings up something called PGT, and the conversation can get a little overwhelming. Three types, different abbreviations, and a lot of medical context to process all at once. Most people walk away with a general sense that it has something to do with testing embryos, but the differences among PGT-A, PGT-M, and PGT-SR are not always explained in a way that actually sticks. So here is a clearer way to think through it.
Preimplantation genetic testing, at its most basic level, is a way of examining embryos created through IVF before they are transferred to the uterus. This helps to check whether they carry certain chromosomal or genetic issues. This matters because many embryos with chromosomal problems either fail to implant, lead to early miscarriage, or result in pregnancies affected by conditions like Down syndrome or Turner syndrome. These are a few things that a couple would want to know about and factor into their decisions. The test itself involves taking a small number of cells from the embryo, usually around day five, and sending that sample to a genetics laboratory for analysis.
What PGT-A Is Actually Checking
PGT-A, where the A stands for aneuploidy, is the most commonly recommended type. Aneuploidy simply means an abnormal number of chromosomes, either too many or too few, and it is far more common than most people expect, particularly in embryos from women over 35. A normal human embryo should have 46 chromosomes arranged in 23 pairs, and when that count is off, the embryo is less likely to result in a healthy pregnancy. PGT-A screens all 23 pairs of chromosomes in a single test to identify which embryos have the correct number, and those are the ones prioritized for transfer. IVF consultations where multiple embryos are available, and the couple needs a way to determine which one to transfer.
A positive PGT-A result does not automatically mean all other embryos are healthy in every other way; it specifically addresses chromosomal count and structure, not gene-level mutations. That distinction is important when thinking through which type of PGT actually fits the situation.
PGT-M, PGT-SR, and When Each One Applies
PGT-M is a different kind of test altogether, targeted at couples who already know they carry or are affected by a specific single-gene disorder, which is a condition caused by a mutation in one particular genFe rather than a chromosomal number problem. Conditions like cystic fibrosis, sickle cell anemia, spinal muscular atrophy, or Duchenne muscular dystrophy fall into this category, and if one or both parents are carriers, there is a defined statistical risk that any embryo they create could inherit that mutation and be affected. PGT-M is designed precisely for this situation, and it requires a preparatory workup before the IVF cycle begins so the lab can develop a test specific to the family’s mutation.
For carrier screening, done before the IVF process, couples can understand their risk profile before deciding whether PGT-M is warranted at all. It is a step that many fertility specialists recommend before jumping into treatment, especially if there is a family history of a known genetic condition.
PGT-SR, on the other hand, is for a specific group of patients in which one or both parents carry a structural rearrangement in their chromosomes, typically a balanced translocation or inversion. A balanced translocation means a section of one chromosome has swapped places with a section of another, but both pieces are present, so the parent is usually healthy and unaware of it until they face repeated miscarriages or implantation failures. The rearrangement becomes a problem when chromosomes are passed to an embryo, because the result can be an unbalanced version with missing or extra genetic material. PGT-SR screens embryos for these imbalances to identify those that are structurally sound for transfer.
MedGenome offers all three types of pgt testing using next-generation sequencing technology, which allows all 23 pairs of chromosomes to be assessed in a single run with 100% sensitivity for aneuploidy detection and 99.98% specificity. Results are typically available within 10 days.
How to Think About Which One Applies
The distinction between the three types becomes clearer once you consider which specific concern is driving the conversation. If the concern is about the overall chromosomal health of embryos, particularly with advanced maternal age, repeated IVF failures, or prior miscarriages with no known genetic cause, PGT-A is the relevant test. If the concern is a known inherited condition that the couple or one partner carries, PGT-M is what addresses that. And if there has been a history of pregnancy loss and chromosomal structural abnormalities have been identified in either parent, PGT-SR is the one worth discussing with the treating doctor.
It is also worth noting that in some situations, more than one type may be recommended together, particularly PGT-A alongside PGT-M or PGT-SR, since each type checks for different things and they are not mutually exclusive. The right combination depends on the couple’s specific reproductive history and genetic background, which is why a genetic counseling session before and after pgt testing can make a real difference in how results are interpreted and what comes next.