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GENETIC TESTING

Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR)

PGT-SR is an optional test for embryos created through IVF when an egg or sperm provider carries a structural chromosome rearrangement. It looks for missing or extra chromosome material related to that known rearrangement.

A carrier is often healthy, but some eggs or sperm can contain an unbalanced amount of chromosome material. PGT-SR can provide more information before embryo transfer, but it cannot test for every genetic condition or guarantee pregnancy or a healthy baby.

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At a glance

Quick Facts About PGT-SR

Get a clear overview of what PGT-SR is and what happens before testing begins.

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What It Evaluates

Looks for missing or extra chromosome material related to a known structural rearrangement.

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Who It's For

May be considered when an egg or sperm provider carries a balanced translocation, inversion, or another testable rearrangement.

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What to Expect

The genetics laboratory reviews the carrier’s chromosome report before IVF to confirm that testing is feasible.

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Limitations

Some methods cannot distinguish embryos with a typical chromosome arrangement from balanced-carrier embryos.

Disclaimer: This information is for educational purposes only and is not a substitute for personalized medical care or genetic counseling.

overview

What is PGT-SR?

Preimplantation genetic testing for structural rearrangements, or PGT-SR, examines embryo samples for chromosome imbalances related to a known rearrangement in an egg or sperm provider.

Chromosomes are packages of DNA that contain our genes. A structural rearrangement means that chromosome material has changed position or organization. The overall amount of genetic material can remain balanced in the carrier, so the person often has no related health concerns.

Eggs or sperm from a carrier can still receive an unbalanced combination of chromosome material. An embryo may then have a missing segment, an extra segment, or both. These differences can affect implantation, pregnancy development, miscarriage risk, or a future child’s health.

PGT-SR can only be performed on embryos created through in vitro fertilization (IVF). It does not change an embryo’s DNA.

PGT-SR differs from PGT-A, which screens embryos for chromosome-number differences without requiring a known parental rearrangement. It also differs from PGT-M, which targets a specific single-gene condition.

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indications for testing

Who may consider PGT-SR?

PGT-SR may be discussed after chromosome testing identifies a structural rearrangement in a person providing eggs or sperm. Examples include:

  • A balanced reciprocal translocation
  • A Robertsonian translocation
  • An inversion that the genetics laboratory can evaluate
  • An insertion, deletion, duplication, or another structural finding that may create unbalanced embryos
  • A previous pregnancy or child with an unbalanced chromosome rearrangement
  • Recurrent pregnancy loss linked to a confirmed parental chromosome finding
  • An egg or sperm donor with a known structural rearrangement

Recurrent pregnancy loss alone does not establish a need for PGT-SR. A confirmed chromosome rearrangement is usually required. A genetic counselor can review the exact report, explain the reproductive risks, and determine whether a PGT laboratory can test the finding.

the process

How PGT-SR Works

PGT-SR requires special planning before an IVF cycle begins. Illume’s fertility specialists, genetic counselors, embryologists, and an outside genetics laboratory work together to coordinate the process.

READING the REPORT

Understanding Your PGT-SR Results

Terminology and result categories vary by laboratory, but reports may include the following.

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Normal or Balanced

The tested sample shows no detectable missing or extra chromosome material related to the familial rearrangement. Some laboratories group embryos with a typical chromosome arrangement and balanced-carrier embryos together.

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Unbalanced

The tested sample shows missing or extra chromosome material related to the structural rearrangement. The possible effect depends on the chromosomes involved and the size and location of the imbalance.

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Unrelated Finding

If the test includes broader chromosome screening, the report can identify a chromosome-number or segmental finding unrelated to the known rearrangement. The laboratory’s terminology and reporting policies determine how these findings appear.

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Inconclusive

The PGT laboratory could not confidently classify the sample.

Poor DNA quality, low DNA quantity, contamination, or other technical factors may sometimes lead to an inconclusive result.

Rebiopsy may be an option in some cases.

Important Note

Ask whether the selected PGT-SR method can distinguish a typical chromosome arrangement from the same balanced rearrangement carried by the egg or sperm provider. Many copy-number methods cannot make that distinction. A balanced-carrier embryo is usually expected to be healthy, but it could face the same reproductive risks later in life.

what's possible

Benefits & Limitations of PGT-SR

Learn what PGT-SR can and cannot determine.

Chromosome Balance

Identifies embryo samples with missing or extra chromosome material related to the known rearrangement.

Informed Transfer Planning

Adds chromosome information to embryo development and grading when deciding which embryo may be considered for transfer.

Lower Transmission Risk

May reduce the chance of transferring an embryo with an unbalanced form of the familial rearrangement.

Insight Before Transfer

Provides information before embryo transfer rather than waiting for pregnancy chromosome testing.

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Limited Test Scope

PGT-SR does not assess every gene, chromosome condition, birth defect, or health concern.

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Case-Specific Feasibility

Very small segments, uncertain breakpoints, and complex rearrangements can fall outside a laboratory method’s detection limits.

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No Pregnancy Guarantee

A normal or balanced result does not guarantee successful implantation, pregnancy, live birth, or a healthy baby.

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Limited Embryos

Some IVF cycles do not produce an embryo with a result that supports transfer under the agreed treatment plan.

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PGT-SR Accuracy & Safety

Important Considerations

Understanding genetic risk

How can a balanced rearrangement affect embryos?

A person with a balanced rearrangement usually has all the expected chromosome material. Some pieces are simply organized differently. That arrangement often has no effect on the carrier’s health.

During egg or sperm formation, the rearranged chromosomes must separate. The resulting egg or sperm can contain:

  • A typical chromosome arrangement
  • The same balanced rearrangement as the carrier
  • An unbalanced arrangement with extra or missing chromosome material

After fertilization, an embryo with extra or missing chromosome material may not implant, may lead to pregnancy loss, or may result in a child with a chromosome condition. The outcome depends on the exact rearrangement and amount of chromosome material involved.

The proportion of normal, balanced, and unbalanced embryos varies widely. A simple percentage cannot describe every translocation or inversion. Each embryo represents a separate chromosome event, so one IVF cycle may not match the expected distribution.

Age at egg retrieval, ovarian reserve, fertilization, blastocyst development, and unrelated chromosome findings can further affect the number of embryos available for transfer.

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common questions

FAQs About PGT-SR

Get answers about balanced rearrangements, costs, results, and prenatal confirmation.

How much does PGT-SR cost?

Can a healthy person carry a balanced translocation?

Can PGT-SR prevent every miscarriage?

Can PGT-SR tell whether an embryo is a balanced carrier?

Do I need a karyotype before PGT-SR?

Does PGT-SR include PGT-A?

Can PGT-SR be performed on embryos that are already frozen?

What happens if no normal or balanced embryos are available?

Is PGT-SR diagnostic?

Can PGT-SR test every structural chromosome rearrangement?

get expert guidance

Is PGT-SR right for you?

Our reproductive endocrinologists and in-house genetic counselors work closely with specialized genetics laboratories to review structural chromosome rearrangements and determine whether PGT-SR is feasible.

If a balanced translocation, inversion, or related chromosome change is found, your Care Team will explain the result, expected risks, anticipated costs, and alternatives. At Illume, you will always receive clear, compassionate, and non-directive guidance.

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