What Is PGT-A?

PGT-A (Preimplantation Genetic Testing for Aneuploidy) — commonly called “third-party IVF.”

Process:

  • IVF/ICSI fertilization
  • Culture embryos to blastocyst stage (day 5–6)
  • Biopsy 5–10 trophectoderm cells
  • High-throughput sequencing/chip to detect chromosome numbers
  • Transfer only chromosomally normal (euploid) embryos

Goal: Reduce miscarriage rate, improve per-transfer success.

Real-World Benefit of PGT-A

PGT-A’s value depends on your embryo abnormality rate:

Population Embryo abnormality rate PGT-A value
<35 years 30–40% Low (anomaly rate not high)
35–37 years 40–50% Medium (consider)
38–40 years 55–65% High (recommended)
41–42 years 70–80% Very high (strongly recommended)
>42 years >85% Complex (may have no normal embryos)
Recurrent miscarriage n/a High (rule out chromosomal causes)
Repeated IVF failure n/a Medium (rule out embryo causes)

Decision Tree: Should You Do PGT-A?

Step 1: Age

Age <35
  ├─ No recurrent loss/failure → Usually not needed
  └─ Recurrent loss or failure → Recommended (rule out embryo causes)

Age 35–37
  ├─ Embryo count ≥5 → Recommended (screens out 30–50% abnormal)
  └─ Embryo count <3 → Not recommended (sample too small, misdiagnosis risk)

Age 38–40
  └─ Embryo count ≥3 → Strongly recommended

Age >40
  ├─ Embryo count ≥3 → Recommended (but accept risk of "no normal embryos")
  └─ Embryo count <3 → Discuss with doctor (may do fresh transfer)

Step 2: Miscarriage History

  • No miscarriages → Low PGT-A value
  • 1 early miscarriage → Low PGT-A value (common occurrence)
  • 2+ early miscarriages → High PGT-A value (recurrent embryo abnormalities possible)
  • 1+ late miscarriage → Very high PGT-A value

Step 3: Previous IVF Failure

  • No failures → PGT-A unnecessary
  • 1 failure, embryo quality unknown → PGT-A optional
  • 2+ failures → High PGT-A value (rule out embryo causes)

Step 4: Family Genetic History

  • No chromosomal abnormality history → Standard PGT-A suffices
  • Chromosomal abnormality history (e.g., Robertsonian translocation) → Need PGT-SR (structural), not just PGT-A
  • Single-gene disease history (cystic fibrosis, thalassemia) → Need PGT-M (monogenic); requires longer prep time

Real Limitations of PGT-A

1. No 100% Health Guarantee

PGT-A detects chromosome number abnormalities (e.g., trisomy 21), but cannot detect:

  • Single-gene disorders (cystic fibrosis)
  • Multifactorial disorders (autism, diabetes susceptibility)
  • Microdeletions/microduplications (some covered by PGT-SR)
  • Developmental issues acquired later

PGT-A-normal embryos still have ~1–3% abnormal live birth rate (mosaic embryos, test error).

2. Mosaic Embryos — A Handling Dilemma

  • Mosaic: some cells chromosomally normal, some abnormal
  • Rate: ~5–15% of PGT-A results
  • Handling:
    • Some clinics: discard
    • Some clinics: consider transfer (with full disclosure)
    • Latest trend: prioritize low-level mosaics (<20% abnormal)

3. Potential Biopsy Damage

  • Controversy: biopsy may damage some trophectoderm cells
  • Latest evidence: minimal impact on embryo development (ASRM 2020 report)
  • Still advised: only biopsy when necessary, avoid unnecessary biopsies

4. Time and Cost

Item US UK
PGT-A per embryo $1,500–3,000 £1,500–2,500
6 embryos $9,000–18,000 £9,000–15,000
Cycle extension +2–4 weeks +2–4 weeks
All-embryo freeze required Yes Yes

5 Major Misconceptions About PGT-A

❌ “PGT-A is third-party IVF, must be better than first/second generation”

Reality: PGT-A doesn’t improve egg/sperm quality — it only tests existing embryos. If you have few embryos (2–3), PGT-A may leave you with none usable.

❌ “PGT-A guarantees no miscarriage”

Reality: PGT-A reduces miscarriage from chromosomal causes, but miscarriage has many causes:

  • Immune factors (antiphospholipid syndrome, NK cells)
  • Endometrial factors (adhesions, thin lining)
  • Hormonal/metabolic (thyroid, diabetes)
  • Anatomical (cervical insufficiency)

❌ “Advanced maternal age must do PGT-A”

Reality: Embryo abnormality rate is high at 40+, but:

  • You may have no normal embryos (all abnormal)
  • Some doctors prefer multiple stimulations + transfers rather than relying on PGT-A
  • It’s a tradeoff: discard all vs. transfer directly

❌ “Fresh transfer doesn’t need PGT-A”

Reality: PGT-A requires frozen embryos to await results, so PGT-A + fresh transfer is not compatible.

❌ “PGT-A-tested embryos are guaranteed normal”

Reality: PGT-A tests trophectoderm cells (future placenta), not inner cell mass (future fetus). Rarely, the two differ (mosaicism), causing “test normal but birth abnormal.”

Final Recommendations by Population

30, First IVF, No Miscarriage History

  • Embryo count ≥5: PGT-A optional
  • Embryo count <3: Not recommended

35, First IVF, No Miscarriage History

  • Embryo count ≥5: PGT-A recommended
  • Embryo count 3–5: Consider
  • Embryo count <3: Not recommended

38, No Miscarriage History

  • Embryo count ≥3: PGT-A strongly recommended

32, 2 Recurrent Miscarriages

  • PGT-A recommended (rule out chromosomal causes)
  • Simultaneously rule out maternal factors (antiphospholipid, thyroid, immune)

40, Repeated IVF Failure

  • Embryo count ≥3: PGT-A optional, but accept “no normal embryos” risk
  • Embryo count <3: Discuss “direct transfer” with doctor

Family Chromosomal Abnormality History

  • Not PGT-A, but PGT-SR
  • Requires longer prep (2–3 months for custom probes)

Family Single-Gene Disease History

  • Not PGT-A, but PGT-M
  • May need more embryos (accuracy requirement)
  • 3–6 months prep work

4 Key Questions for Your Doctor

  1. “In my situation, how many embryos would PGT-A likely screen out?” — abnormality estimate
  2. “If all embryos are abnormal, what’s the next step?” — alternatives
  3. “How does your clinic handle mosaic embryos?” — clinic policy
  4. “If I skip PGT-A, what’s the success rate and risk of direct transfer?” — comparison

Summary

PGT-A is a powerful IVF tool, but not a cure-all. Its value is highest for older patients, recurrent loss/failure populations; limited for younger, first-IVF patients.

Core decision principle: More embryos = PGT-A more worthwhile; Fewer embryos = more caution.

Remember: PGT-A doesn’t improve egg quality — only tests existing embryos. When embryos are scarce, multiple stimulations to bank embryos may be more effective than PGT-A.