What Is PGT-A and Should You Test Embryos?

PGT-A or preimplantation genetic testing for aneuploidy is a screening procedure performed during IVF where embryologists biopsy 5-10 cells from the outer layer of a day 5-6 blastocyst and test them for extra or missing chromosomes using next-generation sequencing. Embryos with the correct 46 chromosomes are prioritized for transfer while aneuploid embryos are excluded reducing miscarriage risk and increasing implantation rates to nearly 70%.

According to Dr. Hrishikesh Pai, renowned IVF Doctor in India, “Testing embryos before transfer takes the guesswork out of selection because chromosomally normal embryos implant better and miscarry less regardless of how good they look under a microscope.”

Embryo reaches blastocyst on day 5 or 6. That’s about 100-200 cells. Embryologist lasers off 5-10 cells from the trophectoderm which is the outer shell that becomes the placenta. The part that becomes the baby doesn’t get touched. Cells ship to a genetics lab. Results in 1-2 weeks. Embryos sit frozen the whole time.

• Biopsy Process: Laser-assisted technique pulls 5-10 trophectoderm cells from each blastocyst. Less than 1% chance of damaging the embryo when done by someone who’s done thousands of these at a specialized fertility treatment center. Inner cell mass stays completely intact
• What It Detects: All 23 chromosome pairs get screened. Extra chromosome. Missing chromosome. Either one flags the embryo as aneuploid. Trisomy 21 and trisomy 18 and monosomy X are the most common findings. Mosaic embryos with a mix of normal and abnormal cells get their own separate category
• Accuracy: 98-99% for whole chromosome aneuploidy using next-generation sequencing. False positives happen but rarely. The issue is mosaicism where the cells they biopsied from the outside don’t perfectly match what’s happening inside the rest of the embryo
• Results Timeline: 1-2 weeks for the genetics lab to run the analysis. Euploid means normal and cleared for transfer. Aneuploid means abnormal and not transferred. Mosaic sits in the middle and some clinics will transfer low-level mosaics after careful counseling with the patient

Embryos stay vitrified the whole time results are pending. When they come back you schedule a frozen transfer cycle which is a separate process entirely and more about that is on the IVF treatment page.

Over 35 and your embryos have a 30-60% chance of being aneuploid. Over 40 that jumps past 80%. A 2026 study looking at 13,000 frozen transfers found PGT-A bumped live birth rates up by 15% for women under 38 and by nearly 30% for women over 40. Under 35 with lots of good blastocysts though. The math changes and the benefit gets harder to justify.

• Women Over 35: 30% aneuploidy at 35. Over 60% at 40. Past 80% by 42. PGT-A takes per-transfer live birth from roughly 35% up to 60% or higher through IVF treatment because you’re only putting back embryos that have the right number of chromosomes
• Recurrent Miscarriage: 50-80% of first-trimester losses come down to chromosomal problems in the embryo. Screen those out before transfer and the miscarriage rate goes from 30-40% down to under 10% which is why couples who keep losing pregnancies see the biggest benefit from PGT-A
• Repeated IVF Failure: Two transfers failed with embryos that looked perfect on camera. Could be that they were chromosomally abnormal the whole time and nobody could tell from morphology alone. PGT-A catches what the microscope misses
• Women Under 35: Big NEJM trial in 2021. Women under 37 with 3 or more blastocysts. PGT-A didn’t improve cumulative live birth rates. What it did was reduce the number of transfers needed to get pregnant. But at ₹50,000-₹1,00,000 per cycle that trade-off doesn’t always make financial sense

Yes it adds cost and yes every embryo gets frozen. But ask any couple who went from three failed transfers to a successful pregnancy after PGT-A and the answer is always the same. More about egg freezing and preservation timing is covered separately.

Dr. Hrishikesh Pai has been doing this for over 40 years. MD and FRCOG (UK-HON) and MSc (USA) and FCPS and FICOG. He started the Bloom IVF Group and the count is past 25,000 IVF cycles across eight centers. Lilavati Hospital Mumbai and DY Patil Navi Mumbai and Fortis in Delhi and Gurgaon and Mohali. His labs run Life Whisperer AI for picking the best embryos.

Hormonal workups and imaging and tubal checks happen before anything gets recommended. FIGO World Congress keynote speaker. BBC World Service feature on egg freezing.

References

1. PGT-A efficacy across maternal ages – Fertility 2026 Abstract
2. Clinical application of preimplantation genetic testing – National Library of Medicine