Genetic abnormalities do not equate to “infertility,” but they may be associated with recurrent miscarriages, embryonic arrest, and repeated IVF failures. This article explains in layman's terms the types of genetic abnormalities, who should consider PGT, the process involved, common misconceptions, and potential risks to aid in treatment decisions.

I) Clarifying the Concept: What Are “Genetic Abnormalities”?

In clinical practice, the term “genetic abnormalities” commonly refers to three major categories:

Chromosomal number abnormalities: Such as embryos having an extra or missing chromosome (aneuploidy). These issues are associated with risks of embryo implantation failure, early miscarriage, and fetal demise.

Chromosomal structural abnormalities: Examples include balanced translocations, Robertsonian translocations, inversions, etc. While the parents may appear clinically healthy, embryos formed from their genetic material are more prone to unbalanced chromosomal combinations, which can adversely affect pregnancy outcomes.

Monogenic disease-related variants: If one or both partners carry certain disease-causing variants (e.g., related to thalassemia, spinal muscular atrophy), the risk of offspring inheriting the condition may increase. Genetic counseling is necessary to assess whether PGT-M is appropriate.

Expert Note: Medical practice prioritizes “clear medical indications.” While both involve “genetic abnormalities,” management approaches differ significantly: Chromosomal issues typically require PGT-A/PGT-SR; single-gene disorder risks necessitate PGT-M and genetic counseling.

II) Who Should Prioritize Screening for “Genetic Abnormalities”?

The following groups are clinically more frequently advised to undergo systematic genetic evaluation (this does not mean everyone requires PGT, but rather that information should be gathered first):

History of recurrent miscarriage/embryonic arrest: A significant proportion of early pregnancy losses are associated with embryonic chromosomal abnormalities; authoritative clinical guidelines indicate that approximately half of early pregnancy losses are related to embryonic chromosomal abnormalities.

Recurrent IVF implantation failure or repeated cycle failure: Comprehensive evaluation is required, considering age, embryo quality, uterine factors, immune/coagulation status, etc. “Genetic abnormalities” represent only one potential clue.

Known chromosomal structural abnormalities in either partner (e.g., balanced translocation carriers): The more common strategy involves considering PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) or selecting an appropriate prenatal diagnosis pathway as advised by the physician.

Advanced maternal age during pregnancy preparation/IVF: Research aligns with clinical knowledge—embryo aneuploidy rates increase with maternal age. Recent IVF/PGT studies also confirm this age-related trend.

Family history of specific genetic disorders or affected offspring: Typically requires genetic counseling for risk stratification to determine if PGT-M or other approaches are necessary.

Expert Note: Relying solely on “genetic abnormalities” as the sole explanation risks overlooking other common factors (endometrial environment, hydrosalpinx, sperm DNA fragmentation, endocrine issues, etc.). A more rational approach is: conduct stratified assessment first, then decide whether to proceed with PGT.

III) How to Choose the Technology: What Issues Do PGT-A, PGT-M, and PGT-SR Address?

Many conflate “PGS/PGD.” The current standard classification is:

PGT-A (Aneuploidy Screening)    Screens embryos for chromosomal number abnormalities    Aneuploidy-related issues (more pronounced with age)    Not a “universal screening”; evidence for outcome improvement and suitability require physician assessment

PGT-M (Single Gene) Targets embryos with known monogenic disease risks    Families with identified pathogenic variants/carriers    Requires prior family validation, probe/site design, and genetic counseling

PGT-SR (Structural Rearrangement)    For carriers of chromosomal structural abnormalities    Balanced translocations/inversions, etc.    Detection limitations and embryo mosaicism may still occur

Expert Note (Key Highlight): PGT-A helps screen for risks of chromosomal number abnormalities but does not guarantee live birth. Suitability, expected benefits, and costs require comprehensive assessment based on age, past outcomes, and laboratory conditions.

IV) 6 High-Frequency Q&As: Addressing Common Pitfalls

Q1: Does a “genetic abnormality” diagnosis mean no hope?

Don't jump to conclusions. First determine the type of abnormality (numerical, structural, monogenic) and whether it's definitively linked to adverse pregnancy outcomes. Many “carriers” are healthy individuals who simply require more rigorous fertility planning and prenatal/embryo-stage testing strategies.

Q2: Does recurrent miscarriage always indicate embryonic chromosomal issues?

Not necessarily. However, clinical guidelines indicate a significant proportion of early pregnancy losses are linked to embryonic chromosomal abnormalities, which is why genetic evaluation is often included in recurrent miscarriage assessments.

Q3: Does PGT-A guarantee prevention of miscarriage?

PGT-A aims to reduce adverse outcomes caused by obvious aneuploidy, but it does not cover all causes (e.g., uterine factors, immune/coagulation issues, embryo developmental dynamics, microdeletions/microduplications, random events). Regarding “who benefits most,” documents from organizations like ASRM emphasize the need for evidence-based and individualized assessment.

Q4: Does PGT “harm embryos”?

The current standard practice is blastocyst-stage trophoblast biopsy, which is more technically mature than earlier-stage biopsies. However, all procedures carry inherent technical risks and depend on laboratory proficiency. ESHRE best practice guidelines emphasize quality management, follow-up, and standardized protocols.

Q5: What if the report mentions “mosaicism”?

Mosaicism represents a complex scenario. Management depends on the laboratory reporting threshold, mosaicism proportion, involved chromosomes, medical history, and the number of viable alternative embryos. In most cases, personalized discussion with genetic counseling and the fertility center is required, rather than relying on one-size-fits-all advice found online.

Q6: What is the typical progression when encountering “genetic abnormalities” during IVF in Beijing?

The pathway generally follows: Fertility clinic evaluation → Genetic counseling → Selection of PGT type (if needed) → Establishing testing protocol and informed consent → Proceeding with ovarian stimulation/egg retrieval/embryo culture and biopsy → Deciding on transfer and follow-up after report release (specific steps may vary by institution).

V) Process Breakdown: 6 Steps from Identifying “Genetic Abnormalities” to Treatment Implementation

Determine Abnormality Type & Evidence Level: Was it incidentally discovered during a physical exam, or identified after recurrent miscarriages? Does the report originate from a certified genetic laboratory?

Genetic Counseling & Risk Stratification: Integrate family history, past pregnancy outcomes, and both partners' test results onto a unified “risk map.”

Decide Whether to Proceed with PGT:

- Predominantly numerical abnormality risk (especially age-related) → Discuss PGT-A indications and expected benefits

- Clear monogenic disease risk → PGT-M (typically requires family validation/site design)

- Chromosomal structural abnormality carriers → PGT-SR or alternative strategies

IVF/ICSI + Embryo Culture: Select fertilization method and culture strategy based on sperm/egg quality.

Blastocyst biopsy + laboratory testing + report interpretation: Focus on test coverage, failure/no-result sample rates, and rules for interpreting mosaicism.

Transfer and prenatal management: Even after PGT, physicians may recommend dual verification with prenatal screening/diagnosis (due to inherent technical limitations).

Expert Note: The most overlooked step in the process is Step 2—genetic counseling. Many “detours” arise not from technical limitations, but from unclear indications, undefined goals, and ambiguous interpretation of results.

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