PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements)

What Is PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements)?

PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) is an advanced genetic screening technique used in IVF (in vitro fertilization) to identify embryos that are chromosomally balanced or unbalanced due to parental structural chromosome rearrangements, such as translocations or inversions. By analyzing embryos before transfer, PGT-SR aims to reduce the risk of miscarriage, failed implantation, or passing on chromosomal abnormalities known to cause infertility or genetic disorders. This testing is especially recommended for individuals or couples with a known balanced chromosomal rearrangement identified on karyotype.

Preimplantation genetic testing for structural rearrangements is increasingly used to help intended parents with a history of recurrent miscarriages, infertility, or chromosomal translocations select embryos most likely to result in a healthy, ongoing pregnancy.

Key Takeaways

PGT-SR screens IVF embryos for unbalanced chromosomal rearrangements before uterine transfer.
It is especially recommended for people with known translocations, inversions, or other chromosomal abnormalities detected by karyotype.
The main goal is to lower miscarriage risk and improve the chances of a healthy pregnancy.
PGT-SR can distinguish between balanced, unbalanced, and normal embryos, but cannot typically detect single-gene disorders unless combined with other testing.
Common structural rearrangements include reciprocal translocations, Robertsonian translocations, and chromosome inversions.
PGT-SR can be combined with PGT-A (for aneuploidy) or PGT-M (for monogenic conditions) for comprehensive screening.
The procedure involves IVF, embryo biopsy (often at the blastocyst stage), and specialized genetic analysis.
Not all embryos from carriers of balanced rearrangements will be suitable for transfer; many will be unbalanced.
The use of PGT-SR can increase the odds of a successful IVF outcome for affected individuals but may not guarantee pregnancy.
Costs for PGT-SR can be significant and vary by clinic, location, and additional testing required.

What Does PGT-SR Mean in Fertility and Reproductive Health?
How Does PGT-SR Work in the IVF Process?
Who Should Consider PGT-SR? (Risk Factors & Indications)
Types of Chromosomal Structural Rearrangements Detected by PGT-SR
Balanced vs. Unbalanced Translocations: Why Does It Matter?
PGT-SR vs. PGT-A: What’s the Difference?
What Is the PGT-SR Process Step by Step?
PGT-SR Success Rates and Outcome Expectations
PGT-SR Cost: What to Expect
Potential Risks, Limitations, and Ethical Considerations of PGT-SR
Frequently Asked Questions About PGT-SR
References and Further Reading
Disclaimer

What Does PGT-SR Mean in Fertility and Reproductive Health?

Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) refers specifically to the genetic testing of embryos created via IVF to detect chromosomal abnormalities resulting from structural changes in chromosomes known as translocations (reciprocal or Robertsonian) or inversions. These structural rearrangements can lead to embryos with missing or extra portions of chromosomes, which may cause miscarriage, IVF failure, or genetic disorders.

For many individuals, a balanced translocation is detected through karyotype analysis after experiencing infertility or recurrent miscarriages. A person with a balanced rearrangement has a normal amount of genetic material, but it's abnormally arranged. While the carrier themselves is often healthy, their eggs or sperm may produce embryos with an abnormal chromosomal complement.

By identifying embryos that are either chromosomally normal or balanced (like the carrier parent), PGT-SR aims to select those most likely to result in a healthy, ongoing pregnancy. PGT-SR is sometimes referred to by older terms like "preimplantation genetic diagnosis for translocations," but PGT-SR is now the preferred terminology.

How Does PGT-SR Work in the IVF Process?

PGT-SR is performed as part of an IVF cycle. The process includes:

Ovarian stimulation in the partner with ovaries.
Egg retrieval and fertilization to create embryos.
Embryo culture to the blastocyst stage (typically day 5–7).
Embryo biopsy, wherein a few cells are gently removed from each embryo.
Genetic analysis of biopsied cells using techniques like next-generation sequencing (NGS) or array comparative genomic hybridization (aCGH).
Embryo selection, where only embryos identified as chromosomally normal or balanced are considered for transfer.

The PGT-SR assay is custom designed based on the precise chromosomal rearrangement(s) identified in the parent’s karyotype. The laboratory evaluates whether each embryo is:

Chromosomally normal
Chromosomally balanced (has the same rearrangement as the parent, but no gain/loss of genetic material)
Chromosomally unbalanced (has extra or missing chromosome parts due to the rearrangement)

Key Point: Only embryos with a normal or balanced chromosomal structure are suitable for transfer, as unbalanced embryos have a high risk of miscarriage or severe developmental issues.

Who Should Consider PGT-SR? (Risk Factors & Indications)

PGT-SR is recommended for individuals and couples in specific situations, including:

One or both partners carry a balanced chromosomal translocation (reciprocal or Robertsonian)
One or both partners have a chromosome inversion
History of recurrent miscarriages with identified chromosomal rearrangement
Abnormal karyotype in one partner following evaluation for infertility, recurrent loss, or a child with unbalanced chromosomal findings
Known risk of transmitting structural chromosomal abnormalities to offspring

Scenario Example: A couple experiences three consecutive miscarriages. Karyotyping reveals one partner carries a Robertsonian translocation. Their doctor recommends IVF plus PGT-SR to increase the odds of a healthy pregnancy.

Other indications for PGT-SR may include:

Previous child or pregnancy affected by a structural chromosome imbalance
Unexplained repeated IVF failures with suspicion of underlying chromosomal rearrangement

Types of Chromosomal Structural Rearrangements Detected by PGT-SR

PGT-SR is designed to detect unbalanced chromosome complements created by parental rearrangements such as:

Rearrangement Type	Description	Example
Reciprocal Translocations	Exchange of segments between non-homologous chromosomes	t(2;8)(p12;q24)
Robertsonian Translocations	Fusion of two acrocentric chromosomes at the centromere	rob(13;14)(q10;q10)
Pericentric Inversions	Inversion including the centromere (spans both arms)	inv(9)(p12q13)
Paracentric Inversions	Inversion within one chromosome arm (does not include centromere)	inv(3)(p21q21)
Marker or Ring Chromosomes	Other complex rearrangements	marker chromosome, ring chromosome

Reciprocal Translocations: Segments from two different chromosomes swap places. Balanced carriers are healthy but can create unbalanced gametes.
Robertsonian Translocations: Two acrocentric chromosomes (chromosomes 13, 14, 15, 21, or 22) join. Carriers appear healthy but have increased risk for trisomy or monosomy in offspring.
Inversions: A chromosome segment is flipped in orientation. Carriers are typically healthy, but some gametes may end up missing or duplicating regions.

Did you know? The most common Robertsonian translocation involves chromosomes 13 and 14.

Balanced vs. Unbalanced Translocations: Why Does It Matter?

A balanced chromosomal translocation or inversion means all critical genetic material is present but arranged differently. The carrier may have no health problems. However, during gamete creation (egg or sperm), the chromosomes can segregate abnormally, leading to eggs or sperm with too much or too little genetic material.

Balanced Embryo: Inherits either the normal chromosome set or the balanced rearrangement from the parent. This embryo has normal copy numbers of all important genes.
Unbalanced Embryo: Inherits an abnormal combination of chromosomes, leading to extra/missing genetic material (partial trisomy or monosomy).

Moving forward with embryo transfer in IVF, only balanced or normal embryos are recommended to maximize success rates and minimize miscarriage risk.

PGT-SR vs. PGT-A: What’s the Difference?

While both PGT-SR and PGT-A are types of preimplantation genetic testing, they have different purposes:

Feature	PGT-SR	PGT-A
Full Name	Preimplantation Genetic Testing for Structural Rearrangements	Preimplantation Genetic Testing for Aneuploidy
Detects	Unbalanced structural changes (translocations, inversions)	Whole chromosome gains/losses (aneuploidy)
Designed for	Known parental chromosomal rearrangement	Anyone, esp. over 35, recurrent IVF failure
Customization	Highly customized to parent’s karyotype	Standardized
Can detect single-gene mutations?	No	No
Utilized when	Karyotype abnormality found in parent(s)	Universal/screening, age, history, etc.

The two tests can be used together: PGT-SR for identifying embryos with abnormal structural chromosomes and PGT-A for general aneuploidy screening.

What Is the PGT-SR Process Step by Step?

Here is the typical timeline and process for PGT-SR in an IVF cycle:

Parental Karyotype Analysis
- Both partners undergo blood karyotype testing to identify whether a structural rearrangement exists and specify its exact breakpoints.
Genetic Counseling
- A certified genetic counselor or REI (Reproductive Endocrinologist) discusses the risks and benefits of PGT-SR, as well as alternative options.
IVF Cycle and Ovarian Stimulation
- The partner with ovaries undergoes hormonal stimulation to produce multiple eggs.
Egg Retrieval and Fertilization
- Eggs are retrieved and fertilized in the lab with sperm.
Embryo Culture
- Embryos are cultured to the blastocyst stage (day 5–7).
Embryo Biopsy
- A few cells from each blastocyst are sampled for genetic analysis.
Custom Genetic Probe/Assay Design
- The IVF lab tailors genetic assays (NGS/aCGH/FISH) based on the specific translocation or inversion found in the parent(s).
Genetic Testing and Analysis
- Biopsied cells are analyzed for unbalanced rearrangements and, potentially, for aneuploidy as well.
Embryo Selection
- Only balanced or normal embryos are chosen for transfer or cryopreservation.
Embryo Transfer
- A single healthy embryo is transferred to the uterus in a prepared cycle.
Pregnancy Testing and Follow-Up
- Standard care resumes with pregnancy testing and monitoring.

Key Point: Accurate parental karyotyping and genetic counseling are required before starting a PGT-SR cycle.

PGT-SR Success Rates and Outcome Expectations

What Are the Success Rates of PGT-SR?

The main goal of PGT-SR is to reduce miscarriage risk and increase the likelihood of a live birth for those with chromosomal rearrangements. Success rates with PGT-SR are generally reported as:

Reduced rates of miscarriage (compared to non-tested embryos from carriers)
Ongoing pregnancy rates after transfer of balanced/normal embryos are similar to general IVF success rates for individuals of the same age group1

Reference Table — Approximate Live Birth Rates per Transfer by Age

Patient Age (years)	Live-Birth Rate per Embryo Transfer (PGT-SR) [estimates]
<35	45–65%
35–37	35–50%
38–40	25–40%
41–42	10–25%

Did you know? Many PGT-SR carriers produce a higher proportion of unbalanced embryos, so more IVF cycles may be needed to find a transferable embryo—especially if both partners are carriers.

Success Factors

Younger maternal age leads to higher embryo yield and transfer rates
Fewer balanced/normal embryos are typically available to carriers of complex rearrangements
Combining PGT-SR with PGT-A may improve overall selection quality

Realistic Expectations

Not all IVF cycles will yield transferable embryos; some cycles may result in only unbalanced embryos.
Additional cycles may be needed, especially if the parent’s rearrangement is complex.

PGT-SR Cost: What to Expect

PGT-SR may significantly increase the cost of an IVF cycle. Here’s a breakdown of typical costs involved:

Cost Component	Approximate Range (USD)
IVF cycle (without PGT-SR)	$12,000–$18,000
PGT-SR lab/testing fee	$3,000–$8,000 (per cycle/tested batch)
Initial probe setup (if needed)	$0–$2,000 (one-time)
Embryo biopsy and freezing	$2,000–$4,000
Medication costs	$3,000–$8,000
Genetic counseling	$200–$500 (per session)

Insurance: Most insurance does not cover PGT-SR, though select states or employer plans may offer partial coverage for genetic testing when indicated.
Financing: Some clinics/labs offer package pricing or payment plans.
Additional cycles: Multiple cycles may increase costs if no transferable embryo is found in the first round.

Potential Risks, Limitations, and Ethical Considerations of PGT-SR

While PGT-SR is a powerful tool for certain intended parents, it is important to consider its limitations and potential downsides:

Potential Risk or Limitation	How to Reduce/Address
False-positive/false-negative results	Use accredited labs and expert interpretation; confirm with prenatal testing
No transferable embryos after biopsy	Counseling on realistic expectations; consider donor gametes as contingency
Procedural risks (IVF, biopsy)	Experienced IVF team and embryologists
Limited scope (cannot detect all types of genetic/epigenetic issues)	Combine with PGT-A/PGR-M if indicated
Emotional, financial burden	Support from counselors and realistic expectations

Key Point: Even with PGT-SR, confirmatory prenatal diagnostic testing (like CVS or amniocentesis) is recommended for all pregnancies.

Ethical Considerations

PGT-SR does not eliminate all risks; some minor chromosomal imbalances may escape detection.
Some couples may face moral or religious concerns about embryo selection/discard.
PGT-SR is not recommended merely for family balancing or non-medical reasons.

Frequently Asked Questions About PGT-SR

What does PGT-SR mean in fertility treatment?

PGT-SR stands for Preimplantation Genetic Testing for Structural Rearrangements, a screening of embryos for chromosomal abnormalities caused by parental structural rearrangements, such as translocations and inversions. It is used in conjunction with IVF to improve the likelihood of a healthy pregnancy for carriers of these rearrangements.

How is PGT-SR different from PGT-A or PGT-M?

PGT-SR detects unbalanced chromosomes resulting from structural rearrangements, while PGT-A screens for overall chromosome number (aneuploidy), and PGT-M detects single-gene disorders. PGT-SR is customized to the parental rearrangement, while PGT-A is broader, and PGT-M targets a specific gene mutation.

Who should undergo PGT-SR testing?

Anyone whose karyotype indicates a balanced translocation, inversion, or similar rearrangement is a candidate for PGT-SR, especially if they have a history of infertility or recurrent miscarriages. Couples with a previous child or pregnancy affected by a chromosomal disorder may also benefit.

Can PGT-SR prevent miscarriages?

PGT-SR cannot prevent all miscarriages, but it significantly reduces the risk by identifying and excluding embryos that are unbalanced and likely to fail implantation or end in miscarriage.

What types of chromosome rearrangements does PGT-SR detect?

PGT-SR identifies unbalanced embryos from parental reciprocal translocations, Robertsonian translocations, pericentric/inversions, and some other chromosomal markers/rings.

What is a balanced translocation, and why does it matter in IVF?

A balanced translocation is a chromosome abnormality where material has been exchanged but no genetic information is lost or gained. The carrier is usually healthy but may produce eggs or sperm with extra or missing chromosome fragments, increasing the risk of miscarriage or genetic disorders in offspring.

How many embryos tested in PGT-SR are usually suitable for transfer?

This depends on the precise rearrangement and parental age, but data suggests only 15–40% of embryos from a translocation carrier will be balanced or normal and suitable for transfer2.

Does using PGT-SR guarantee a healthy baby?

No, PGT-SR greatly reduces certain genetic risks but cannot test for all conditions. Confirmatory prenatal testing is still advised.

How long does PGT-SR take from start to finish?

From initial consultation and karyotyping to completed genetic analysis of embryos in an IVF cycle, the process may take 2–3 months. Embryos may be frozen until genetic results are complete.

How much does PGT-SR cost?

PGT-SR typically adds $3,000–$8,000 to the cost of an IVF cycle, not counting additional IVF, medication, or embryo storage fees.

Is PGT-SR covered by insurance?

In most regions, PGT-SR is not routinely covered, but some cases may qualify for partial reimbursement, especially with a documented genetic indication.

Is PGT-SR safe for embryos?

Current research suggests embryo biopsy for PGT-SR is safe in experienced labs, but any manipulation may have theoretical risks. Large studies show no increase in birth defects or developmental problems after blastocyst biopsy3.

What happens if no balanced or normal embryos are found in PGT-SR?

If a cycle yields no transferable embryos, options include trying another IVF cycle, using donor gametes, or considering adoption or embryo adoption.

Can PGT-SR be used for single gene disorders?

PGT-SR is not used for single gene disorder detection but may be combined with PGT-M for families with both a structural rearrangement and known gene mutation.

How reliable is PGT-SR?

PGT-SR is highly reliable in accredited labs, but no form of PGT can detect all types of genetic or chromosomal abnormalities. Rare technical limits or mosaicism can affect results.

What follow-up testing is recommended after successful IVF with PGT-SR?

Standard prenatal diagnostic testing—like chorionic villus sampling (CVS) or amniocentesis—should be performed for confirmation of embryo genetic status.

How does age impact PGT-SR success?

Fertility declines with age regardless of PGT-SR use; older egg providers have fewer and lower quality embryos, further reducing the odds of finding a transferable one per cycle.

Does carrier status of both partners change the PGT-SR approach?

If both partners are carriers, genetic counseling is vital to determine risks and design the most accurate testing strategy for their unique scenario.

Can PGT-SR detect small chromosomal changes?

PGT-SR is optimized for large chromosomal rearrangements; some small imbalances or subtelomeric changes may escape detection, so limitations must be discussed with a genetics specialist.

What questions should I ask my doctor about PGT-SR?

Ask about your individual karyotype, the likelihood of finding transferable embryos, anticipated costs and success rates, technical limitations, counseling and support, and what happens if PGT-SR finds only unbalanced embryos.

References and Further Reading

Harton GL, et al. Importance of pretreatment counseling in carriers of chromosome rearrangements undergoing preimplantation genetic diagnosis. https://pubmed.ncbi.nlm.nih.gov/24777912/
Scriven PN, et al. Efficacy of preimplantation genetic diagnosis for carriers of reciprocal and Robertsonian translocations: a systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/24951114/
Green KA, et al. The clinical significance of embryo biopsy for preimplantation genetic screening at the blastocyst stage: a systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/26803756/
American Society for Reproductive Medicine (ASRM): Preimplantation Genetic Testing Fact Sheet. ASRM PGT Fact Sheet
ESHRE PGT Consortium. Data collection XII: PGT for chromosomal structural rearrangements. https://pubmed.ncbi.nlm.nih.gov/31410969/
Natera: PGT-SR Clinical Overview. https://www.natera.com/
March of Dimes: Chromosome Translocations https://www.marchofdimes.org/find-support/topics/birth-defects/chromosome-translocations
Centers for Disease Control (CDC): ART and Genetic Testing https://www.cdc.gov/art/key-terms.html
Ferraretti AP, et al. Preimplantation genetic testing: ESHRE Survey. https://pubmed.ncbi.nlm.nih.gov/31136441/
Resources for genetic counseling: National Society of Genetic Counselors https://www.nsgc.org/

Disclaimer

This article is for informational and educational purposes only and does not constitute medical or mental health advice. It is not a substitute for speaking with a qualified healthcare provider, licensed therapist, or other professional who can consider your individual situation.