Two tests, names one letter apart. It is easy to see why couples mix up PGT-A vs PGT-M, or assume one covers the other. They sound alike, and both check embryos during IVF, but they answer completely different questions. One counts chromosomes. The other looks for a single inherited condition a family already knows about. Knowing which is which, and which one applies to you, clears up a lot of confusion at the start of treatment.
Preimplantation Genetic Testing
Both tests belong to the same family, called preimplantation genetic testing, or PGT. The idea behind it is straightforward. During IVF, embryos grow in the lab for about five to six days. The embryologist gently removes a few cells from each embryo and sends them for genetic analysis, while the embryos stay frozen and stored. The results help the team decide which embryo to transfer. PGT does not change an embryo. It only gives information about it beforehand.
PGT-A Testing in IVF
PGT-A stands for preimplantation genetic testing for aneuploidy. Aneuploidy means an embryo has too many or too few chromosomes. A healthy embryo carries 46 chromosomes, arranged in 23 pairs. An extra or missing chromosome is one of the most common reasons an embryo fails to implant, or a pregnancy ends in miscarriage. PGT-A counts the chromosomes in each embryo and flags the ones with the right number. It does not read individual genes. It checks the overall count.
The value of PGT-A is still debated among specialists, and it appears to help some groups more than others. This is why a specialist advises on whether it earns its place in a given cycle, rather than adding it by default.
PGT-M Testing
PGT-M stands for preimplantation genetic testing for monogenic disorders. It looks for one specific gene change that a family is already known to carry, such as the fault behind thalassemia, cystic fibrosis, sickle cell disease, or spinal muscular atrophy. This is the real contrast with PGT-A. PGT-M examines a single gene instead of counting chromosomes. It is a targeted test, built around one known condition, so the lab first develops a test specific to that family’s mutation before the IVF cycle starts. That build adds time worth planning for.
Difference Between PGT-A and PGT-M
PGT-A:
- Counts the embryo’s chromosomes to check the number is right
- Screens for extra or missing chromosomes, a common cause of miscarriage
- Suited to older mothers, repeated miscarriage, or failed IVF cycles
- Uses a standard panel, so no custom build is needed
PGT-M:
- Looks for one specific inherited condition the family already carries
- Screens for a single known gene fault, such as thalassemia or cystic fibrosis
- Suited to families with a known single-gene condition in their history
- Needs a family-specific test built first, which adds time before the cycle
Who Needs PGT-A or PGT-M
The two point to different situations. PGT-A is usually considered for couples where chromosome errors are more likely: older mothers, those with repeated miscarriage, or those who have had repeated failed IVF cycles. PGT-M is for families with a clearly identified inherited risk. That includes couples where both partners carry the same recessive condition, where one partner carries a dominant one, or a couple has already had a child affected by a single-gene disorder. Neither is a routine test for everyone. A genetic counsellor or fertility specialist confirms whether either one fits a couple’s history.
Choosing between PGT-A vs PGT-M, or working out whether either is needed, starts with the right information rather than a procedure. The fertility team at 9M Fertility offers both tests along with genetic counselling, and can look at your history to explain which one, if any, makes sense for you. If genetic testing is on your mind, that conversation is the place to begin: https://www.9mfertility.com/contact-us/
