Preimplantation Genetic Testing for Aneuploidy (PGT-A) or for Monogenic disorders (PGT-M) refers to a procedure where embryos obtained through an IVF cycle are evaluated for genetic disorders prior to implantation.  The purpose of these tests are very different from each other. PGT-A is to identify embryos affected by chromosomal abnormalities that will affect an embryo by chance. PGT-M is to help prevent certain diseases or disorders from being passed on to the child from the parent. In most cases for PGT-M, the female, male, or both partners have been genetically screened and identified to be carriers of potential problems.

The Ottawa Fertility Centre works with a reputable genetics lab in Detroit, Michigan called Cooper Genomics . Patients of the Ottawa Fertility Centre now have access to important genetic testing prior to an embryo transfer.

 

PGT-A

What information will PGT-A provide?

• Full aneuploidies (complete extra or missing chromosome)
• Partial aneuploidies (extra or missing pieces of chromosomes)

 

What information will PGT-A NOT provide?

• Balanced chromosomal rearrangements, where the correct amount of genetic tissue is present
• Very small deletions or duplications of genetic material
• Autism
• Intellectual disability
• Birth defects
• Single gene disorders

 

What are the possible results of PGT-A?

• Euploid – No abnormalities detected
• Mosaic – Full or partial chromosome missing or extra in SOME cells but not all
• Non-mosaic deletion/duplication – Partial chromosome missing or extra in all cells
• Aneuploid - Full chromosome extra or missing
•  Inconclusive/No results

 

PGT-A Pros & Cons

Benefits	Risks/Limitations
Reduces miscarriages	Chance of no normal embryos
Reduces aneuploidy detection during or after pregnancy	Test error (false negatives & positives)
Less wasted time if high embryo number	Uncertain/unclear results
	Risk of biopsy/freezing
	Does not increase overall fertility

 

Who might choose to pursue PGT-A?

Reasons a couple might choose to use PGT-A can vary:

• Reduce chance of a multiple pregnancy
• Reduce time to a live birth
• Reducing risk of spontaneous abortion (miscarriage)
• Use of a gestational carrier
• Embryo banking for the future

 

PGT-M

What information will PGT-M provide?

• Presence or absence of a specific genetic difference (“mutation”) that runs in the family

What information will PGT-M NOT provide?

• Autism/Intellectual disability/Birth defects UNLESS it is caused by a specific gene being tested
• Other single gene disorders
• Chromosomal aneuploidy (but this can be added with PGT-A)

What are the possible results of PGT-M?

Familial genetic variant is not identified (Not affected)

Familial genetic variant is identified (Affected)

However, it is important to consider that the meaning of “affected” can be different. Some family members may have the same mutation but individuals may be affected differently, such as:

• Severity
• Age of onset
• Effect on different sexes differently
• Be a carrier of a condition versus affected by it

 

PGT-M Pros & Cons

Benefits	Risks/Limitations
Identify embryos affected by a known familial genetic difference to avoid transfer of an “abnormal” embryo	Requires customized test development for EVERY patient
	Often involves relatives
	Longer timeline (may take several months)
	Not always possible to identify the genetic variant
	Variants of unknown significance (VUS) – mutations that we don’t know what the clinical outcome may be

 

Any couple at risk for passing on a genetic disease or condition could benefit from PGT-M. Possible candidates include:

• Carriers of sex-linked genetic disorders.
• Carriers of single gene defects.
• Those with chromosomal disorders.
• Women experiencing recurrent pregnancy loss associated with chromosomal concerns.

Summary

• PGT enables couples to pursue biological children who might not have been able to do so otherwise.
• Performing PGT-A or M prior to implantation can reduce the use of amniocentesis later in pregnancy.
• PGT helps reduce the chance of conceiving a child with a genetic factor. However, it cannot completely eliminate this risk. In some cases, further testing during pregnancy is recommended to ascertain if a genetic factor is still possible.
• Information and Resources

 

Contact your physician at the Ottawa Fertility Centre for more information and to determine whether or not PGT-A/PGT-M is an appropriate treatment option for you.