PGT: Genetic Testing of IVF Embryos Explained
PGT (Preimplantation Genetic Testing) analyses embryos created during IVF before they are transferred to the uterus. It helps identify chromosomally normal embryos most likely to implant successfully — reducing failed transfers and miscarriage risk for the patients who need it most.
What Is Preimplantation Genetic Testing?
During an IVF cycle, embryos develop in the laboratory for 5 days until they reach the blastocyst stage. Before one is transferred to the uterus, PGT analyses the genetics of each embryo using cells biopsied from the outer layer (trophectoderm — which becomes the placenta, not the baby).
The goal is to identify euploid embryos — embryos with the correct number of chromosomes (46) — which are far more likely to implant and less likely to miscarry than aneuploid (abnormal) embryos. PGT does not prevent all pregnancy losses or guarantee a live birth, but it significantly improves the probability of each transfer being successful.
⚠️ Important distinction: PGT selects the best embryo from those already produced in your IVF cycle. It does not produce more embryos or create new genetic material. If all embryos from a cycle are aneuploid, PGT means none will be transferred — requiring another stimulation cycle or a change of approach.
Types of PGT — PGT-A, PGT-M, and PGT-SR
PGT-A
Preimplantation Genetic Testing for Aneuploidies
What it tests: Tests all 46 chromosomes for extra or missing copies (aneuploidy). Examples: Down syndrome (trisomy 21), Turner syndrome (45X), and other non-viable chromosomal errors.
Who needs it: Women over 37, recurrent miscarriage (2+), recurrent failed IVF cycles, previous aneuploid pregnancy.
PGT-M
Preimplantation Genetic Testing for Monogenic Disorders
What it tests: Tests for a specific single-gene disease that one or both parents carry — e.g. beta-thalassaemia, sickle cell disease, cystic fibrosis, Huntington's disease, BRCA1/2 mutations.
Who needs it: Couples who are carriers of serious heritable single-gene disorders. Requires a custom genetic probe designed specifically for your family's mutation.
PGT-SR
Preimplantation Genetic Testing for Structural Rearrangements
What it tests: Tests for chromosomal structural rearrangements — translocations and inversions — that one parent is known to carry. These can cause recurring miscarriage or failed implantation.
Who needs it: Couples where one partner has a known chromosomal translocation or inversion (identified by karyotyping). Often discovered after multiple miscarriages.
PGT-A — Chromosomal Screening in Detail
PGT-A is the most commonly used type of PGT in India. It screens all 23 pairs of chromosomes for numerical abnormalities using Next Generation Sequencing (NGS), which can detect extra or missing chromosomes with high accuracy.
Why Chromosomal Abnormalities Matter
| Age | % Eggs Chromosomally Normal | % Aneuploid Embryos (approx) | Clinical Impact |
|---|---|---|---|
| Under 30 | 70–80% | 20–30% | Low risk; PGT-A rarely needed routinely |
| 30–34 | 60–70% | 30–40% | Moderate risk; consider with recurrent failure |
| 35–37 | 50–60% | 40–50% | Growing risk; PGT-A adds meaningful value |
| 38–40 | 35–50% | 50–65% | High aneuploidy; PGT-A strongly recommended |
| 41–42 | 20–35% | 65–80% | Majority abnormal; PGT-A identifies the rare viable |
| 43+ | <20% | >80% | Most embryos aneuploid; donor egg often more efficientt |
✅ What PGT-A Improves
- Implantation rate per transfer: 60–70% (euploid) vs 40–50% (untested)
- Miscarriage rate: drops from ~30–40% to ~5–10%
- Number of transfers needed — often just one euploid embryo succeeds
- Reduction in chromosomally abnormal pregnancies (e.g. Down syndrome)
⚠️ What PGT-A Does NOT Do
- Does not increase the number of embryos you produce
- Cannot detect all single-gene disorders (PGT-M needed for those)
- Cannot guarantee a live birth — other factors affect implantation
- May result in no embryos to transfer if all are aneuploid
Who Should Consider PGT?
Women Over 37–38
Chromosomal abnormality rates rise sharply after 37. PGT-A identifies the viable minority of embryos, allowing targeted single embryo transfer with higher success per attempt.
Recurrent Miscarriage (2+ losses)
50–60% of recurring miscarriages are caused by chromosomal errors in the embryo (not uterine or immune factors). PGT-A screens these out before transfer.
Failed IVF Cycles (2+ without explanation)
If previous cycles produced embryos that were transferred but failed to implant without a clear reason, aneuploidy is one of the most common causes. PGT-A is the diagnostic step.
Carriers of Single-Gene Disorders
If you or your partner carry thalassaemia, BRCA1/2, sickle cell, cystic fibrosis, or another serious heritable condition — PGT-M selects embryos unaffected by that mutation.
Known Chromosomal Translocation
If karyotyping has identified a balanced translocation in either partner, PGT-SR selects unaffected embryos, dramatically reducing miscarriage risk from that cause.
Previous Chromosomally Abnormal Pregnancy
If a previous pregnancy was diagnosed with trisomy 21, trisomy 18, or other chromosomal condition, PGT-A is recommended to screen future IVF embryos.
⚠️ PGT-A is NOT routinely recommended for all IVF patients. For women under 35 with no history of miscarriage or failed cycles and a good prognosis, the additional cost and the risk of embryo biopsy damage (small but present) may outweigh the benefit. Your reproductive endocrinologist will advise based on your specific profile.
The PGT Process — Step by Step
🔬 What is a mosaic result? Some embryos show a mixed chromosomal signal — some cells normal, some abnormal. These are called mosaic embryos. They can sometimes lead to healthy pregnancies but carry a higher risk than fully euploid embryos. Your specialist will explain the clinical implications of any mosaic results and whether transfer is appropriate in your specific case.
PGT Cost in India
PGT is an add-on to an IVF cycle — not a standalone procedure. Costs are in addition to your base IVF cycle (₹1.5L–₹2.8L). PGT-A pricing in India is typically per batch of embryos, not per embryo.
| PGT Type | Cost in India | Includes | Turnaround |
|---|---|---|---|
| PGT-A | ₹30,000 – ₹60,000 | NGS chromosomal analysis of all biopsied embryos from one cycle | 7–14 days |
| PGT-M | ₹60,000 – ₹1,20,000 | Custom probe design for specific mutation + analysis; family-specific | 4–6 weeks (probe design) + 7–14 days (analysis) |
| PGT-SR | ₹60,000 – ₹1,00,000 | Chromosomal structural rearrangement analysis; custom linkage study | 4–6 weeks + analysis |
| Additional FET cycle (if needed) | ₹30,000 – ₹60,000 | Uterine preparation and embryo transfer; no re-stimulation | 4–6 weeks |
Costs vary by genetics laboratory partner and city. Confirm exact pricing and whether the genetics lab is in-house or external (which affects turnaround).
Frequently Asked Questions — PGT
What is PGT in IVF?＋
PGT (Preimplantation Genetic Testing) is genetic analysis performed on Day 5 (blastocyst-stage) embryos during an IVF cycle before transfer. A few cells are biopsied from the outer layer of each embryo and analysed in a genetics lab. Results identify chromosomally normal (euploid) embryos, which are significantly more likely to implant successfully and carry a lower miscarriage risk.
Does PGT damage the embryo?＋
The biopsy removes 5–10 cells from the trophectoderm (outer layer, which becomes the placenta — not the baby). Multiple published studies show no significant increase in the risk of birth defects, developmental problems, or health issues in children born after PGT. The risk of biopsy-related embryo damage is estimated at 1–2% per embryo in experienced labs.
Does PGT-A improve success rates?＋
PGT-A improves the implantation rate per transfer (from ~40–50% untested to ~60–70% for euploid embryos) and significantly reduces miscarriage risk. However, it does not produce more viable embryos — it only identifies which of your existing embryos are chromosomally normal. If all embryos are aneuploid, no transfer occurs from that cycle.
What happens if all embryos are abnormal?＋
If PGT-A results show all retrieved embryos are aneuploid, no transfer is possible from that cycle. Your specialist will review the stimulation protocol and discuss options: another retrieval cycle, banking additional embryos before retesting, or for older patients, considering donor egg IVF which virtually eliminates the chromosomal aneuploidy problem (as donor eggs are from young donors).
How long does the PGT process take?＋
PGT-A results typically take 7–14 days after biopsy. During this time, embryos are frozen (vitrified). Once results are received, a frozen embryo transfer (FET) cycle is scheduled — usually 4–6 weeks after. PGT-M and PGT-SR require a custom probe designed for your specific mutation (4–6 weeks initially), then standard 7–14 days for analysis.
Is PGT worth the extra cost?＋
This depends entirely on your clinical profile. For women over 38, patients with recurrent miscarriage, or those with known genetic carrier status — the evidence strongly supports PGT's value in reducing failed cycles and emotional burden. For young women under 35 with no adverse history going through their first IVF cycle, the clinical benefit of PGT-A is more limited and the cost may not be justified. Discuss with your reproductive endocrinologist based on your specific test results and history.
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