If you have experienced repeated implantation failure (RIF), you may be exploring genetic testing options for embryos. Two tests often discussed are PGT-A and PGT-SR. Both are forms of preimplantation genetic testing, but they look for different types of chromosomal issues. This article explains the difference, how they might be used in RIF, and what to keep in mind.
At a glance
- PGT-A screens embryos for an abnormal number of chromosomes (aneuploidy).
- PGT-SR checks for structural rearrangements of chromosomes, such as translocations.
- Both tests require IVF and a biopsy of the embryo.
- Neither test guarantees pregnancy or a healthy baby.
What is PGT-A?
PGT-A (preimplantation genetic testing for aneuploidy) is a test that looks at the number of chromosomes in an embryo. Humans typically have 46 chromosomes in each cell. An embryo with too many or too few chromosomes is called aneuploid. Most aneuploid embryos fail to implant or result in miscarriage. PGT-A aims to identify embryos with the correct number of chromosomes, which may improve the chances of implantation.
What is PGT-SR?
PGT-SR (preimplantation genetic testing for structural rearrangements) is used when one or both parents carry a structural chromosomal rearrangement, such as a balanced translocation or inversion. These rearrangements do not usually affect the parent’s health, but they can lead to embryos with unbalanced chromosomes, which may cause implantation failure or miscarriage. PGT-SR identifies embryos with a normal or balanced chromosomal structure.
Key differences between PGT-A and PGT-SR
| Aspect | PGT-A | PGT-SR |
|---|---|---|
| What it screens for | Abnormal number of chromosomes (aneuploidy) | Structural rearrangements (e.g., translocations, inversions) |
| Who might consider it | People with RIF, advanced maternal age, or previous miscarriages | Couples where one partner has a known structural rearrangement |
| How it works | Biopsied cells are analyzed for chromosome count | Biopsied cells are analyzed for chromosome structure |
| Goal | Select embryos with the correct number of chromosomes | Select embryos with normal or balanced chromosome structure |
How PGT-A might be used in RIF
In RIF, the cause is often unknown. PGT-A may be offered to check whether chromosomal abnormalities in embryos are contributing to implantation failure. If most embryos are aneuploid, transferring a euploid embryo might improve the chance of implantation. However, PGT-A does not address other potential causes of RIF, such as uterine factors, immune issues, or embryo-endometrium interaction.
How PGT-SR might be used in RIF
PGT-SR is typically considered only if a parent is known to carry a structural rearrangement. If you have RIF and a family history of translocations or repeated miscarriages, your doctor may recommend karyotyping (a blood test) for you and your partner. If a rearrangement is found, PGT-SR can help select embryos with a normal or balanced structure.
Limitations of PGT-A and PGT-SR
- Not a guarantee: Even a genetically normal embryo may not implant or lead to a live birth.
- Biopsy risks: Embryo biopsy is invasive and requires skilled laboratory expertise.
- Mosaicism: PGT-A may not always detect mosaicism (a mix of normal and abnormal cells).
- Cost and time: Genetic testing adds to the cost of IVF and may delay embryo transfer.
- Not for everyone: These tests are not necessary for all patients and may not be recommended in every case.
Questions to ask your clinic
- What is your experience with PGT-A and PGT-SR?
- What is the biopsy technique, and how many cells are taken?
- How are results reported, and what do they mean for my embryos?
- What are the costs for the test and the IVF cycle?
- How long will it take to get results?
- What are the alternatives if I do not want genetic testing?
Next steps
- Discuss your history of RIF with your fertility specialist.
- Ask whether genetic testing is appropriate for your situation.
- Consider genetic counseling to understand the implications.
- Review the costs and logistics with your clinic.
- Make an informed decision based on your personal circumstances.
For more information, see our PGT in Thailand guide, explore our guides, or check the FAQ.
Frequently asked questions
Can PGT-A help with repeated implantation failure?
PGT-A may help identify embryos with an abnormal number of chromosomes, which could be a cause of implantation failure. However, it does not address other potential causes, and a normal result does not guarantee pregnancy.
Is PGT-SR only for people with known chromosomal rearrangements?
Yes, PGT-SR is typically recommended when one or both parents carry a structural rearrangement, such as a translocation. If you have RIF and suspect a rearrangement, your doctor may suggest karyotyping first.
What is the difference between PGT-A and PGT-SR?
PGT-A screens for an abnormal number of chromosomes, while PGT-SR checks for structural rearrangements. Both require IVF and embryo biopsy, but they look for different types of chromosomal issues.
Are PGT-A and PGT-SR guaranteed to result in a baby?
No. Genetic testing can help select embryos with a higher chance of implantation, but it does not guarantee pregnancy or a live birth. Other factors also affect success.
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.