Most conversations about preimplantation genetic testing focus on PGT-A, which screens embryos for the correct number of chromosomes. But for a smaller group of women and couples, particularly those with a history of recurrent miscarriage or a known chromosomal translocation, a related but distinct test called PGT-SR, or preimplantation genetic testing for structural rearrangements, may be more relevant to their fertility journey after 35.
PGT-SR is designed specifically to detect embryos affected by structural chromosomal rearrangements, such as translocations or inversions, which can be inherited from a parent who carries a balanced version of the rearrangement without any health effects of their own, but who may pass an unbalanced version to embryos.
Because this type of testing is less commonly discussed than standard aneuploidy screening, many patients encounter the term for the first time only after a difficult diagnostic journey involving recurrent loss and specialized genetic testing. Understanding the basics before that conversation happens, or reviewing them afterward at your own pace, can make the process feel somewhat less overwhelming.
What Research Shows About Structural Rearrangements
According to research indexed through the National Institutes of Health’s PubMed database, balanced chromosomal translocations are carried by an estimated 1 in 500 people, most of whom are unaware because the rearrangement doesn’t typically cause health problems for the carrier. However, when a carrier’s embryos inherit an unbalanced version of the rearrangement, this can contribute to recurrent miscarriage or, less commonly, to a pregnancy affected by a chromosomal condition. This connection is one reason genetic carrier screening is often recommended after recurrent pregnancy loss, discussed in more detail in resources on evaluating recurrent miscarriage after 35.
Who PGT-SR Is Typically Recommended For
PGT-SR is generally recommended for individuals or couples who have undergone karyotype testing and identified a balanced translocation or inversion in one partner, often after experiencing recurrent miscarriage or having a previous pregnancy or child affected by an unbalanced chromosomal rearrangement. It is not a routine part of most standard IVF cycles unless this specific genetic finding is already known.
How the Testing Process Works
The process begins with identifying the specific translocation or inversion through parental karyotype testing, often ordered by a reproductive endocrinologist or genetic counselor after recurrent loss. Once the specific rearrangement is characterized, a custom probe can be developed for that particular chromosomal configuration, which is then used during IVF to test embryo biopsies for balanced or normal chromosome arrangements versus unbalanced ones.
What Results Can and Cannot Tell You
PGT-SR results can help identify embryos that carry an unbalanced version of the known rearrangement, which are generally not selected for transfer due to higher risk of miscarriage or pregnancy complications. However, this testing is specific to the structural rearrangement being screened for and does not evaluate overall chromosome number the way PGT-A does, which is why many clinics combine both PGT-SR and PGT-A when clinically appropriate. Discussing your specific antral follicle count and FSH levels after 35 alongside genetic testing plans can help your care team develop realistic expectations about the number of embryos likely available for testing.
It’s also worth understanding that combining PGT-SR with PGT-A on the same embryo biopsy generally does not require additional biopsy procedures, since both tests can often be performed from the same small tissue sample collected during a single biopsy. This means pursuing both forms of testing typically does not add meaningful additional risk to the embryos themselves, though it may add cost and processing time to your overall cycle timeline.
Emotional Considerations of Genetic Testing
Learning that you or your partner carries a balanced translocation, often only discovered after experiencing pregnancy loss, can bring up complicated feelings, including grief about past losses and anxiety about future attempts. Genetic counseling is typically offered alongside this testing specifically to help process both the technical and emotional dimensions of these findings. Many couples find that understanding the biological explanation behind previous losses, even when it doesn’t undo the grief, provides some clarity moving forward.
Considering the Broader Family Planning Picture
A translocation finding often affects family planning conversations beyond the current IVF cycle. Some couples choose to test remaining frozen embryos from a prior cycle retroactively if PGT-SR becomes available after the fact, though this depends on whether embryos were biopsied at the time of freezing, since re-biopsy is not always feasible or advisable. Others factor the translocation finding into decisions about whether to pursue additional egg retrievals, given that the proportion of balanced versus unbalanced embryos can vary considerably between cycles and does not guarantee a specific number of usable embryos from any given attempt.
For couples who already have living children, a translocation diagnosis sometimes prompts additional testing for those children as well, particularly if there’s a chance the rearrangement could affect their own future fertility. This is a personal decision usually made in consultation with a genetic counselor, weighing the child’s age, the specific rearrangement involved, and the family’s preferences about disclosure and timing of this kind of testing.
It’s also worth noting that insurance coverage for PGT-SR varies significantly and is often handled differently than coverage for PGT-A, given its more specialized and custom nature. Contacting your insurance provider directly, or working with your clinic’s financial counseling team, before starting a cycle that will include this testing can help you understand costs in advance and avoid surprises during an already demanding process.
Frequently Asked Questions
How is PGT-SR different from PGT-A?
PGT-A screens for the overall number of chromosomes in an embryo, while PGT-SR specifically screens for a known structural rearrangement, such as a translocation, identified through prior parental testing.
Do I need PGT-SR if I’ve had a miscarriage?
Not necessarily. PGT-SR is generally recommended only after karyotype testing identifies a specific balanced translocation or inversion in a parent. Your reproductive endocrinologist can help determine if this testing applies to your situation.
Does carrying a balanced translocation mean I can’t have a healthy pregnancy?
No. Many carriers of balanced translocations have healthy pregnancies, sometimes without any fertility treatment at all. PGT-SR is one tool used to help improve the odds of selecting embryos more likely to result in a successful pregnancy.
Is genetic counseling required for this type of testing?
While not always mandatory, genetic counseling is strongly recommended and often built into the process, given the complexity of interpreting these results and their implications for family planning.
Key Takeaways
- PGT-SR screens embryos for known structural chromosomal rearrangements, such as translocations, typically identified after parental karyotype testing.
- This testing is generally recommended for those with a known balanced translocation, often discovered after recurrent miscarriage.
- PGT-SR is distinct from PGT-A and does not evaluate overall chromosome number on its own.
- Genetic counseling is an important part of processing both the technical results and emotional weight of this testing.
- Carrying a balanced translocation does not preclude healthy pregnancy, and PGT-SR is one tool to help inform embryo selection.
Medical Disclaimer
This content is for informational purposes only and does not constitute medical advice. Individual health situations vary significantly. Always consult a qualified healthcare provider before making decisions related to your health, fertility, or pregnancy.
About the Author
Emily Carter is a women’s health writer focused on fertility, pregnancy after 35, and sleep changes in midlife. She writes research-informed, non-alarmist content to help women navigate reproductive and hormonal transitions with clarity and confidence.