PGT-A: Should You Test Your Embryos Before Transfer?
PGT-A (Preimplantation Genetic Testing for Aneuploidy) screens IVF embryos for chromosomal errors before transfer. It is one of the most discussed — and debated — add-ons in modern IVF. This guide explains what it does, who genuinely benefits, and what the evidence says.
What Is Aneuploidy and Why Does It Matter?
Aneuploidy means having the wrong number of chromosomes. Human embryos should have 46 chromosomes (23 pairs). Aneuploid embryos — those with extra or missing chromosomes — either fail to implant, cause early miscarriage, or very occasionally result in conditions such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), or Patau syndrome (trisomy 13).
Aneuploidy rate by maternal age (approximate):
| Age | % Aneuploid Embryos |
|---|---|
| 30 | ~30–35% |
| 35 | ~45–55% |
| 38 | ~60–70% |
| 40 | ~70–80% |
| 43+ | ~85–95% |
This is why IVF success rates decline steeply with age — not because stimulation fails, but because most embryos produced are chromosomally abnormal and cannot implant or sustain a pregnancy.
How PGT-A Works
- Biopsy: On Day 5–6, 5–10 cells are removed from the trophectoderm (the outer cell layer that becomes the placenta) of each blastocyst. The inner cell mass (which becomes the foetus) is not touched.
- Vitrification: All biopsied embryos are immediately frozen.
- Analysis: The biopsied cells are analysed by Next-Generation Sequencing (NGS) to count chromosomes. Results take 7–14 days.
- Results: Each embryo is classified as:
- Euploid (normal): All 46 chromosomes present — eligible for transfer - Aneuploid: Chromosomal error — not eligible for transfer - Mosaic: Mix of normal and abnormal cells — complicated interpretation (see below)
- Transfer: A subsequent frozen embryo transfer cycle. Only euploid (or selected mosaic) embryos are transferred.
Who Genuinely Benefits From PGT-A?
ASRM 2023 identifies the following as the strongest evidence-based indications:
Women over 38: High aneuploidy rates mean most embryos are chromosomally abnormal. PGT-A identifies the minority that are normal — avoiding failed transfers and miscarriages. The most consistent benefit demonstrated in retrospective and prospective data.
Recurrent pregnancy loss (2+ miscarriages): Where aneuploidy is the likely cause, PGT-A reduces the miscarriage rate per transfer from ~40% to ~10% by selecting chromosomally normal embryos. Strong evidence.
Recurrent implantation failure (2+ failed transfers with good-quality blastocysts): Identifies whether the problem is embryo chromosomes or an endometrial/receptivity issue. If all available embryos test aneuploid → age/egg quality is the explanation. If a euploid embryo fails → investigate endometrium (ERA, hysteroscopy, endometritis).
Male factor with very high DNA fragmentation: Elevated paternal DNA fragmentation increases aneuploidy rates. PGT-A selects the normal embryos.
Where PGT-A Is NOT Clearly Beneficial
Younger women (<35) with no prior failed cycles: Most embryos in women under 35 are euploid. Randomly selecting one of multiple blastocysts by grade achieves very similar outcomes to PGT-A selection in this group. Large RCTs (ESTEEM trial, 2021) show PGT-A does not improve live birth rate per started cycle in good-prognosis patients — it redistributes the same success faster (fewer transfers to first live birth, but same cumulative outcome).
Low ovarian reserve with few embryos: If only 1–2 blastocysts are produced per cycle, biopsying them all and finding all are aneuploid leaves nothing to transfer. This cycle provides information but no treatment option. In poor responders, the decision must weigh information gain vs the risk of having no transferable embryos.
The Mosaic Embryo Controversy
Approximately 10–15% of embryos test as mosaic — containing a mixture of euploid and aneuploid cells. This reflects real chromosomal mosaicism or biopsy/technical artefact.
Should mosaic embryos be transferred? Data from multiple centres shows live birth rates of 35–40% per transfer of mosaic embryos — lower than euploid (45–55%) but significantly higher than aneuploid (<5%). Many healthy babies have been born from mosaic embryo transfers.
ASRM 2023 guidance: Mosaic embryos may be transferred after counselling. Clinics vary on their approach — some transfer low-level mosaics routinely; others recommend additional caution.
Cost of PGT-A in India (2025)
| Component | Cost (INR) |
|---|---|
| Biopsy (per embryo) | ₹5,000–₹10,000 |
| NGS analysis (per embryo) | ₹15,000–₹25,000 |
| Total per embryo biopsied | ₹20,000–₹35,000 |
| 4 blastocysts tested | ₹80,000–₹1,40,000 |
This is additive to IVF costs. At ₹80,000–₹1,40,000 for 4 embryos, PGT-A is a significant investment. For younger women (<35) with no prior failures, the cost-to-benefit analysis is less clear than for older patients or those with recurrent failure.
PGT-A Does Not Create Normal Embryos
The most important limitation: PGT-A selects from embryos you already have — it cannot create new ones. If all your embryos are aneuploid, PGT-A tells you this clearly (which has value for decision-making), but it does not provide a euploid embryo to transfer.
Reference: ASRM Practice Committee — Clinical Management of Mosaic Results from PGT-A, 2023. ESTEEM Trial — Preimplantation Genetic Testing for Aneuploidy, Human Reproduction 2021.
Frequently Asked Questions
Does PGT-A improve IVF success rates?▾
It depends who you are. For women over 38, recurrent miscarriage, or recurrent implantation failure, PGT-A significantly reduces time to live birth by avoiding transfers of aneuploid embryos that would have failed. For younger women under 35 with no prior failures, large RCTs show PGT-A does not improve cumulative live birth rates — it just redistributes the same success across fewer transfers.
Is PGT-A safe for the embryo?▾
The trophectoderm biopsy at Day 5–6 is considered safe by ASRM and ESHRE. Thousands of healthy births from biopsied embryos confirm this. The biopsy takes 5–10 cells from the outer cell layer that becomes the placenta — not the inner cell mass that becomes the baby. Vitrification after biopsy adds a small risk of embryo loss (<5%), which must be weighed against the benefit of testing.
What is a mosaic embryo?▾
A mosaic embryo contains a mixture of normal and abnormal cells. About 10–15% of embryos test as mosaic. Mosaic embryos can result in healthy pregnancies — live birth rates per transfer are approximately 35–40% (lower than euploid at 45–55% but much higher than aneuploid at <5%). ASRM 2023 supports transferring low-level mosaic embryos after counselling, when no euploid embryos are available.