PGT Can Test for Both Specific and General Genetic Disorders
Preimplantation Genetic Testing (PGT) encompasses different types that can test embryos either for specific genetic disorders that families are at high risk for (PGT-M) or screen for general chromosomal abnormalities (PGT-A), depending on the clinical indication. 1
Types of PGT and Their Applications
PGT-M: Testing for Specific Known Disorders
PGT for monogenic disorders (PGT-M) is designed to test embryos for specific genetic conditions when couples are known carriers or have a family history of a particular disorder. 1, 2
PGT-M is indicated when one partner has a monogenic disorder, both partners are carriers of the same recessive condition, or the couple has previously conceived or is at high risk of conceiving a child with a specific monogenic disorder that results in death, malformation, or disability 1
This testing requires that the pathogenicity of the gene variant is unequivocal or that linkage markers of the related gene are definite before proceeding 1
PGT-M can be performed for autosomal dominant conditions, autosomal recessive conditions, X-linked disorders, and even for HLA matching to create a "savior sibling" 2, 3
The technique allows direct mutation testing for the specific pathogenic variant(s) that the parents carry, preventing transmission to offspring 4
PGT-A: General Chromosomal Screening
PGT for aneuploidy (PGT-A) screens embryos for general chromosomal abnormalities rather than specific inherited conditions. 5, 3
PGT-A only screens for chromosomal abnormalities and cannot guarantee a completely healthy child, as it does not detect monogenic disorders or conditions caused by de novo mutations 5
This type of testing is used for couples with recurrent miscarriages, advanced maternal age, or unexplained infertility, rather than for specific genetic disease prevention 3
PGT-P: Emerging Polygenic Risk Testing
A newer form called PGT for polygenic conditions (PGT-P) tests for risk of multiple complex disorders simultaneously, though this remains controversial and is not broadly recommended. 1
PGT-P can screen embryos for risk indications of multiple polygenic conditions such as cardiovascular diseases, cancer, diabetes, and even quantitative traits like height 1
This differs fundamentally from PGT-M because it provides risk scores rather than definitive diagnoses, and environmental factors play significant roles in whether these conditions develop 1
The clinical utility remains controversial with uncertain and relatively limited potential gains, and it is currently offered only by commercial entities rather than being implemented in standard healthcare 1
Key Clinical Distinctions
The choice between testing for specific versus general disorders depends entirely on the couple's risk profile and reproductive history. 1, 6
Couples with known carrier status or family history of specific Mendelian disorders should pursue PGT-M for targeted testing of that particular condition 1, 7
Couples without specific genetic risks but with recurrent pregnancy loss or advanced maternal age may be candidates for PGT-A to screen for general chromosomal abnormalities 3, 6
PGT-M requires pre-testing and genetic counseling to confirm the specific pathogenic variants and establish testing protocols, whereas PGT-A uses standardized chromosomal screening 1, 2
Important Caveats
Patients must understand that no form of PGT can detect all possible genetic disorders or guarantee a completely healthy child. 5, 6
PGT-M only tests for the specific condition(s) being targeted and will not detect other genetic abnormalities 4
The risk of misdiagnosis cannot be completely eliminated, as diagnosis from single cells remains technically challenging 6
Environmental factors play significant roles in many conditions and traits that PGT cannot account for 5