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GENETIC TESTING

Preimplantation Genetic Testing for Monogenic Conditions (PGT-M)

PGT-M is an optional, targeted test for embryos created through IVF when a specific disease-causing gene change has been identified in a family. It may help reduce the chance of passing that inherited condition to a future child.

Because each PGT-M case is designed around a particular gene change and inheritance pattern, laboratory case review and customized test development generally occur before IVF begins. PGT-M does not test every gene or guarantee pregnancy or a healthy baby.

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At a glance

Quick Facts About PGT-M

Get a clear overview of what PGT-M evaluates and what is required before testing can begin.

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What It Evaluates

Tests embryo samples for a specific gene change associated with an inherited single-gene condition.
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Who It's For

May be considered when a known genetic risk is identified via personal, family, or carrier screening.
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Custom Testing

A specialized lab develops a family-specific test before IVF, sometimes using DNA from relatives.
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Limitations

PGT-M only evaluates the targeted genetic condition and cannot guarantee pregnancy or a healthy baby.

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

overview

What is PGT-M?

Preimplantation genetic testing for monogenic conditions, or PGT-M, tests embryos for a specific inherited condition caused primarily by a change in one gene. These are sometimes called single-gene or Mendelian conditions.

PGT-M may be considered for conditions such as cystic fibrosis, sickle cell disease, spinal muscular atrophy, Huntington disease, or an inherited cancer predisposition associated with a gene such as BRCA1 or BRCA2. The specific familial gene change generally must be identified before testing can be developed.

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

PGT-M is targeted testing, not a broad assessment of every gene or health condition. It is also different from PGT-A, which screens embryos for extra or missing chromosomes.

PGT-M illustration
indications for testing

Who may consider PGT-M?

PGT-M may be discussed when a known genetic change could significantly increase the chance of a child inheriting a specific condition. Examples include:

  • Both genetic parents are carriers of the same autosomal recessive condition
  • One genetic parent has an autosomal dominant condition
  • One genetic parent carries an X-linked condition
  • A previous child or pregnancy was affected by a confirmed single-gene condition
  • A known familial gene variant is associated with a genetic condition or disease predisposition
  • A relevant disease-causing variant has been identified in an egg or sperm donor

PGT-M is usually not recommended when only one genetic parent is a carrier of an autosomal recessive condition and the other has tested negative, since the chance of an affected child is generally very low.

PGT-M for a variant of uncertain significance may have limited value because it is not yet known whether the variant causes disease, and laboratory policies vary. Genetic counseling is especially important in these cases.

the process

How PGT-M Works

PGT-M requires additional planning before an IVF cycle begins. Illume’s genetic counselors, fertility specialists, embryologists, and an outside genetics laboratory coordinate the entire process.

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Genetic Counseling

Your genetic counselor reviews the condition, inheritance pattern, genetic reports, and available family history. A PGT lab then determines whether testing is technically feasible.

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Test Development

The lab develops a custom test (probe) using DNA from the egg and sperm providers or relatives if needed. This process can take several weeks to several months and is usually completed before IVF begins.

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IVF & Biopsy

Eggs are retrieved, fertilized, and monitored in Illume’s laboratory. An embryologist carefully removes a small sample of cells from embryos that reach the blastocyst stage.

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DNA Analysis

The biopsied embryos are frozen and stored at Illume. Cell samples are sent to the genetics lab, which analyzes the targeted variant and may also examine nearby DNA markers.

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Review & Plan

Your genetic counselor explains how each embryo was classified, what the results mean for you, and which embryos may be considered for transfer.

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READING the REPORT

Understanding Your PGT-M Results

Exact terminology may vary by laboratory, but results generally fall into four categories.

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Unaffected

The tested sample does not show the gene variant or combination of variants associated with the targeted condition. The embryo may still be a carrier in some situations.
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Affected or At Risk

The embryo has inherited the gene variant or combination of variants associated with the condition or disease predisposition being tested.
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Carrier

The embryo has inherited a variant associated with a recessive or X-linked condition but is not expected to be affected.
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Inconclusive

The lab could not confidently classify the sample. Poor DNA quality, contamination, or other factors may contribute. Rebiopsy may be an option in some cases.

Important Note

A positive result does not always predict whether symptoms will develop, when they will begin, or how severe they will be. This is particularly important for conditions with reduced penetrance, variable expression, or adult-onset disease risk. Illume’s genetic counselors can explain the findings and help you understand how each result may affect your options.

what's possible

Benefits & Limitations of PGT-M

Learn what PGT-M may help clarify and what it cannot determine.

Targeted Results

Identifies whether the tested embryo sample inherited the specific familial gene variant or combination of variants.

Lower Transmission Risk

May reduce the chance of passing the targeted inherited condition to a future child.

Informed Transfer

Helps patients prioritize embryos for transfer using condition-specific information.

Pre-Pregnancy Insight

Provides genetic information before embryo transfer rather than waiting until pregnancy for diagnostic testing.

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Single Condition

PGT-M evaluates only the targeted gene and does not assess other genetic or health risks.

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No Pregnancy Guarantee

A negative result does not ensure implantation, pregnancy, live birth, or a healthy baby.

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Uncertain Expression

A variant may be detected without predicting severity, onset, or whether symptoms will occur.

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Limited Embryos

Some cycles may not produce an embryo suitable for transfer and not expected to be affected by the targeted condition.

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PGT-M Accuracy & Safety

Important Considerations

Understanding genetic risk

How does inheritance affect PGT-M results?

The proportion of embryos expected to be affected, unaffected, or carriers depends on how the condition is inherited. For an autosomal recessive condition in which both genetic parents are carriers, each embryo generally has:

  • A 25% chance of being affected
  • A 50% chance of being an unaffected carrier
  • A 25% chance of being unaffected and not a carrier

For an autosomal dominant condition in which one genetic parent has one copy of the relevant variant, each embryo generally has a 50% chance of inheriting the variant.

For an X-linked condition, the chance of an embryo being affected or carrying the variant depends on which parent carries the variant, the specific condition, and the embryo’s sex chromosome pattern.

Each embryo represents an independent genetic event, so the results from a particular IVF cycle may not match these expected percentages. Age at egg retrieval, ovarian reserve, fertilization, blastocyst development, and any additional testing can further affect how many embryos are ultimately available for transfer.

These inheritance probabilities describe genetic risk. They don't predict how many eggs, blastocysts, or transferable embryos an individual IVF cycle will produce.

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common questions

FAQs About PGT-M

Learn about PGT-M costs, custom test development, accuracy, and other considerations.

How much does PGT-M cost?

How long does PGT-M probe development take?

Can PGT-M test for any genetic condition?

Can PGT-M be used for BRCA1 or BRCA2?

Is PGT-M the same as genetic carrier screening?

Does PGT-M include PGT-A?

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

What happens to embryos with a positive PGT-M result?

get expert guidance

Is PGT-M right for you?

At Illume Fertility, our reproductive endocrinologists and in-house genetic counselors collaborate with external genetics laboratories to determine whether custom probe development for PGT-M is feasible.

Whether you are responding to carrier-screening results, a personal diagnosis, a known family condition, or a previous affected pregnancy or child, your Care Team will help you understand your options with clear, compassionate, and non-directive guidance.

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