Clinically, PGT (Preimplantation Genetic Testing) includes:

· PGT-A: Aneuploidy screening (chromosomal number abnormalities)

· PGT-SR: Structural rearrangements (translocations/inversions)

· PGT-M: Monogenic disorders (requires customized probe design)

PGT-M is not required for every IVF patient.
It is primarily recommended for families with specific genetic risks:

· Family history of genetic disorders:
One or both partners are known carriers of a monogenic disorder
(e.g., thalassemia, SMA, spinocerebellar ataxia, etc.)

· Previously affected child:
If the first child was born with a genetic disorder, PGD/PGT-M can prevent recurrence in subsequent pregnancies.

I. Conditions Detectable by PGT

🔹PGT-A (Aneuploidy Screening)

· Screens for numerical abnormalities in all 23 chromosome pairs

· Common findings: Trisomy 21 (Down syndrome), Trisomy 18, Trisomy 13, sex chromosome abnormalities

· No customized probe required

· Indications: Advanced maternal age, recurrent miscarriage, recurrent IVF failure

🔹PGT-SR (Structural Rearrangements)

· Detects translocations, inversions, deletions, duplications

· No customized probe required

· Indications: Known chromosomal rearrangement carriers

🔹PGT-M

1. Autosomal Recessive Disorders

· Thalassemia, SMA, Cystic fibrosis

· Common in Taiwan

2. Autosomal Dominant Disorders

· Huntington’s disease, Marfan syndrome

· Clear family inheritance pattern

3.X-linked Disorders

· Hemophilia, Duchenne muscular dystrophy (DMD)

· Higher risk in male offspring

4. Neurodegenerative / Metabolic Disorders

· Spinocerebellar ataxia, inherited metabolic disorders

· Often rare familial diseases

5. Immunologic / Hematologic Disorders

· Severe immunodeficiency, sickle cell disease

· HLA matching possible (savior sibling)

II. Most Common Conditions for PGT-M in Taiwan

III. Customized Probe Design Process (PGT-M Only)

1️⃣Confirm specific mutation (1–2 weeks)

2️⃣Construct family haplotype (2–3 weeks)

3️⃣Design customized assay (2–4 weeks)

4️⃣Laboratory validation (1 week)
Total waiting time: ~6–10 weeks

IV. Estimated Timeline from Treatment Start to Embryo Transfer

V. PGT-M Timeline Overview

Q & A

Q: Why do timelines vary?
A: Because PGT-M requires customized testing.

Q: Why does PGT-M take longer?
A: Because the test is specifically designed for your family’s mutation.

Q: Is it worth the wait?
A: It can reduce 25–50% recurrence risk to 0%.

Clinical Significance of PGT

· PGT can break the cycle of inherited diseases.

· Avoid traumatic termination after prenatal diagnosis.

· Improve implantation and live birth rates by selecting healthy embryos.