At a glance
Understand the difference between PGT-A and PGT-M when you carry a single gene disorder, and learn why PGT-M is often the necessary choice.
PGT-A vs PGT-M: What’s the Difference?
If you carry a single gene disorder (also called a monogenic condition), you may be exploring preimplantation genetic testing (PGT) as part of your IVF journey. Two common types of PGT are PGT-A and PGT-M. While both involve testing embryos created through IVF, they answer different questions.
PGT-A (preimplantation genetic testing for aneuploidy) screens embryos for an abnormal number of chromosomes. It is often used to improve the chances of a successful pregnancy, especially for people of advanced maternal age or those with recurrent miscarriage.
PGT-M (preimplantation genetic testing for monogenic disorders) looks for a specific genetic mutation that causes a particular single gene disorder, such as cystic fibrosis, sickle cell disease, or Huntington’s disease. If you or your partner carry a known mutation, PGT-M can identify embryos that do not inherit the disorder.
For patients with a known single gene disorder, PGT-M is usually the necessary test. PGT-A alone cannot tell you whether an embryo carries your specific mutation. In some cases, both PGT-A and PGT-M may be performed together, but they serve distinct purposes.
At a Glance: PGT-A vs PGT-M
- PGT-A: Checks chromosome number (aneuploidy). Does not test for specific gene mutations.
- PGT-M: Tests for a specific single gene mutation. Requires prior genetic testing of parents and often other family members.
- PGT-SR: Tests for structural rearrangements of chromosomes (e.g., translocations). Sometimes relevant if you also have a chromosome issue.
- Which one?: If you have a known single gene disorder, PGT-M is essential. PGT-A may be added for chromosome screening.
Why PGT-M Is Necessary for Single Gene Disorders
Single gene disorders are caused by mutations in a specific gene. PGT-M is designed to detect whether an embryo has inherited that mutation. Without PGT-M, you cannot know if an embryo is affected by the condition you carry.
PGT-A, on the other hand, only counts chromosomes. An embryo can have a normal number of chromosomes but still carry a disease-causing mutation. Therefore, PGT-A is not a substitute for PGT-M when you have a known monogenic disorder.
In some situations, your clinic may recommend doing both PGT-A and PGT-M. This is because embryos that are free of the mutation may still have chromosome abnormalities that could affect implantation or lead to miscarriage. Combining both tests can provide more complete information, but it also adds complexity and cost.
How PGT-M Works
PGT-M is a multi-step process that begins before you start an IVF cycle. Here is a general overview:
- Genetic counseling and testing: You and your partner will meet with a genetic counselor. The specific mutation must be identified through genetic testing of you, your partner, and sometimes other family members.
- IVF and embryo biopsy: After eggs are retrieved and fertilized, embryos are grown in the lab for several days. A few cells are then removed from each embryo (biopsy).
- Genetic analysis: The biopsied cells are analyzed for the specific mutation. This requires a customized test for your family’s mutation.
- Embryo selection: Embryos that do not carry the mutation are considered for transfer.
Because PGT-M requires a personalized test, it is not a one-size-fits-all procedure. The laboratory needs time to develop and validate the test before your cycle begins.
PGT-A: What It Can and Cannot Do
PGT-A is often used to select embryos with the correct number of chromosomes. It can help reduce the risk of miscarriage due to aneuploidy and may improve the efficiency of IVF by avoiding transfer of embryos that are unlikely to implant.
However, PGT-A does not test for single gene mutations. If you have a known monogenic disorder, PGT-A results will not tell you whether an embryo is affected by that condition. Therefore, PGT-A is not a replacement for PGT-M.
Some patients may choose to have both PGT-A and PGT-M. This can be beneficial because it provides two layers of information: the specific mutation status and the chromosome status. But it also means more testing, which can increase the time and cost of the IVF cycle.
PGT-SR: When Chromosome Structure Matters
PGT-SR (preimplantation genetic testing for structural rearrangements) is used when one or both parents have a chromosomal rearrangement, such as a translocation. This can cause embryos to have missing or extra chromosome segments, leading to miscarriage or birth defects.
If you have a single gene disorder, PGT-SR is not typically needed unless you also have a known chromosomal rearrangement. Your genetic counselor can help determine if PGT-SR is relevant for your situation.
Choosing Between PGT-A and PGT-M in Thailand
If you are considering PGT in Thailand, you will likely work with an IVF clinic that offers genetic testing services. The choice between PGT-A and PGT-M depends on your medical history and genetic status.
For patients with a known single gene disorder, PGT-M is the primary test. PGT-A may be added if you also want chromosome screening. Some clinics may offer a combined approach, but this is not always necessary.
When researching clinics in Thailand, ask about their experience with PGT-M for your specific condition. Not all laboratories may have the capability to develop a customized test for every mutation. It is important to confirm that the clinic can handle your case.
Questions to Ask Your Clinic
Before deciding on PGT, consider asking your clinic the following questions:
- Do you offer PGT-M for my specific single gene disorder?
- How long does it take to develop a personalized PGT-M test?
- Can you perform PGT-A and PGT-M together on the same embryo biopsy?
- What is the success rate for embryos that are free of the mutation?
- What are the limitations of PGT-M? Are there any embryos that may have unclear results?
- What is the cost of PGT-M, and does it include genetic counseling and test development?
Next Steps: Your Checklist
- Confirm your genetic diagnosis and the specific mutation with a genetic counselor.
- Research IVF clinics in Thailand that offer PGT-M for your condition.
- Ask about the laboratory’s experience with your type of mutation.
- Discuss whether PGT-A is also recommended in your case.
- Understand the timeline, including the time needed for test development.
- Clarify all costs and what they include.
PGT is a personal decision. It is not a guarantee of pregnancy or a healthy child, but it can provide valuable information to help you make informed choices. Always consult with your medical team to determine the best approach for your situation.
Frequently asked questions
Can PGT-A detect single gene disorders?
No. PGT-A only checks for an abnormal number of chromosomes. It does not test for specific gene mutations. If you have a known single gene disorder, you need PGT-M to determine whether an embryo carries the mutation.
Is PGT-M necessary if I have a single gene disorder?
Yes, if you want to identify embryos that do not carry the specific mutation causing your disorder. PGT-M is the only type of PGT that tests for a particular monogenic condition. PGT-A cannot provide that information.
Can PGT-A and PGT-M be done together?
Yes, in many cases both tests can be performed on the same embryo biopsy. This provides information about both the specific mutation and chromosome number. However, not all clinics may offer combined testing, so it is important to ask.
How long does PGT-M take in Thailand?
The timeline can vary. PGT-M requires a personalized test to be developed for your family's mutation, which can take several weeks or months. Your clinic can give you a more specific estimate based on your case.
Continue your research
Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.
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