PGT-A (preimplantation genetic testing for aneuploidy) screens IVF embryos for chromosomal abnormalities before transfer. It costs $3,000–$6,000 per cycle (biopsy plus lab analysis). PGT-A improves per-transfer success rates and reduces miscarriage risk, but it does not increase the total number of genetically normal embryos — it identifies the ones you already have. The benefit is clearest for women over 37, those with recurrent loss, or those who want to avoid transferring embryos destined to fail.
- PGT-A tests embryos for the correct number of chromosomes (46). Aneuploid embryos (wrong number) almost always result in failed implantation or miscarriage
- Per-transfer live birth rates with PGT-A-tested euploid embryos are approximately 60–65%, compared to 40–50% without testing
- PGT-A does not increase the number of normal embryos your cycle produces — it reduces failed transfers and miscarriages by avoiding aneuploid embryos
- The test has a small but real false-positive rate (5–10%), meaning some embryos labeled “abnormal” could have resulted in healthy pregnancies
- MIT Technology Review named AI-assisted embryo scoring a 2026 top-10 breakthrough technology, reflecting how rapidly this field is evolving
What PGT-A Tests
Every cell in a healthy human body contains 46 chromosomes (23 pairs). Aneuploidy means an embryo has too many or too few chromosomes. The most well-known aneuploidy is Trisomy 21 (Down syndrome, an extra chromosome 21), but most aneuploidies are not compatible with life and result in failed implantation or early miscarriage.
PGT-A screens for the correct number of all 23 chromosome pairs. It does not test for single-gene disorders (that’s PGT-M) or structural chromosomal rearrangements (PGT-SR).
How the Biopsy Works
On day 5 or 6 of embryo development, the embryologist removes 5–10 cells from the trophectoderm (the outer layer that becomes the placenta, not the inner cell mass that becomes the baby). The biopsied cells are sent to a genetics lab (CooperGenomics, Natera, Igenomix, or others). Results take 1–2 weeks. Meanwhile, the embryos are frozen and stored.
The Evidence: Who Benefits Most?
| Patient Group | Aneuploidy Rate | PGT-A Benefit |
|---|---|---|
| Under 35 | 20–30% of embryos | Modest — most embryos are normal anyway; reduces transfers but may discard viable embryos |
| 35–37 | 30–40% | Moderate — starts to meaningfully reduce failed transfers |
| 38–40 | 50–65% | Strong — avoids transferring the majority-abnormal cohort |
| 41–42 | 65–80% | Strong — identifies the few normal embryos in a mostly abnormal batch |
| Over 42 | 80–90% | Strong per embryo, but fewer embryos to test; some clinics advise against due to yield |
| Recurrent pregnancy loss | Varies | Strong — reduces miscarriage risk significantly |
The Controversy: False Positives and Mosaicism
PGT-A is not perfect. Two issues deserve honest discussion:
False Positives
The biopsy samples the trophectoderm, not the inner cell mass. In approximately 5–10% of cases, the outer cells may show a different chromosomal makeup than the cells that become the baby. This means some embryos labeled “aneuploid” and discarded could have self-corrected and produced healthy pregnancies. This is the strongest argument against universal PGT-A for young patients with many embryos.
Mosaic Embryos
Mosaic embryos contain a mix of normal and abnormal cells. Some mosaic embryos can produce healthy pregnancies, though at lower rates than fully euploid embryos and with slightly higher miscarriage risk. Many clinics now transfer mosaic embryos when no euploid embryos are available, rather than discarding them. Discuss mosaic transfer policies with your RE.
PGT-A costs $3,000–$6,000 per cycle. For a young patient under 35 with 5+ blastocysts, the cost may not be justified — most of those embryos are normal anyway, and the false-positive risk means potentially discarding good embryos. For a 39-year-old with 3 blastocysts, PGT-A may save the emotional and financial cost of 1–2 failed transfers. The calculus is personal, and a good RE will walk you through the math for your specific situation.
AI-Assisted Embryo Scoring: The Next Step
AI-based embryo grading tools are emerging as a complement to (or potential replacement for) PGT-A. MIT Technology Review named AI embryo scoring a 2026 top-10 breakthrough technology. Companies like Alife Health (partnered with US Fertility) and CHLOE by Fairtility use machine learning to analyze time-lapse images of embryo development and predict implantation potential.
The promise: non-invasive embryo selection that avoids the biopsy entirely, eliminating both the false-positive risk and the $3,000–$6,000 cost. The reality in 2026: AI tools are supplemental, not yet a replacement for PGT-A. They can help prioritize which embryo to transfer first but cannot yet match PGT-A’s ability to identify specific chromosomal abnormalities.
For a deeper look at the evidence versus marketing claims, see our AI in IVF article.