What Is PGT-A in IVF?

During IVF, embryos grow in the lab for several days. For PGT-A, an embryologist removes a few cells, usually from the trophectoderm (the outer layer, which ASRM notes contains no cells destined to become the fetus) at the blastocyst stage, and a genetics lab counts the chromosomes. ASRM says next-generation sequencing (NGS) and SNP microarray are now the main platforms, and that labs differ in their protocols and in how they classify results.

In the two large multicenter trials ASRM reviewed, tested embryos were transferred in later frozen-embryo transfer cycles. Your clinic will explain its own timing; the IVF timeline guide covers how testing can add time before transfer.

ASRM, citing national SART data, shows how common testing has become: the share of U.S. IVF cycles using PGT rose from 14% in 2014 to 44% in 2019.

ACOG says the clinical value of PGT-M and PGT-SR "is firmly established," while the role of PGT-A "remains to be determined."

• Euploid: the biopsy showed the expected number of chromosomes.
• Aneuploid: the biopsy showed a missing or extra chromosome.
• Mosaic (intermediate copy number): the biopsy appeared to contain a mix of cells. ASRM says this can reflect true mosaicism but also lab and technical factors, and that mosaic embryos "can implant and generate apparently euploid offspring," though they may implant at lower rates. HFEA says clinics differ in how they test, report and transfer mosaic embryos.
• Segmental: part of a chromosome appeared to be missing or duplicated.
• No result: the sample couldn't be read.

How accurate is it? The biopsy is a few cells, not the whole embryo. ASRM cites a multicenter NGS study in which none of 102 transferred embryos labeled aneuploid led to an ongoing pregnancy, and a SNP-microarray study reporting a 96% positive predictive value. It also cites a case series in which 141 embryos with abnormal results (including mosaic) were transferred and 8 live births followed. ASRM says clinics should have a written policy on what happens to abnormal and mosaic embryos and share it before testing.

Live birth. In the STAR trial (2019, 34 clinics, 661 patients aged 25–40 with at least two blastocysts), ongoing pregnancy rates were similar with and without PGT-A, per embryo transfer (50% vs. 46%) and per patient randomized (41.8% vs. 43.5%). A post hoc look at women 35–40 found a higher rate per transfer (51% vs. 37%) but not per patient randomized. In a 2021 trial in China (1,212 women aged 20–37 with at least three good-quality blastocysts), cumulative live births were 77.2% with PGT-A and 81.8% with conventional IVF; ASRM notes the PGT-A group had only three blastocysts biopsied, which limits the comparison.

Miscarriage. In that 2021 trial, pregnancy loss was 8.7% with PGT-A and 12.6% without, but this didn't translate into more live births. ASRM calls the value of PGT-A for lowering miscarriage "unclear." HFEA, reviewing the evidence for UK patients, rates it green for reducing miscarriage for most patients.

Older patients. ASRM says retrospective studies suggest a benefit in older patients, but the randomized trials enrolled mostly younger, favorable-prognosis patients. HFEA rates the evidence for older women as insufficient (grey).

Recurrent pregnancy loss. ASRM's 2026 opinion says PGT-A "has not been shown to significantly reduce miscarriage or improve live births" compared with expectant management, and that for women over 40 with a proven aneuploid miscarriage it is "reasonable to discuss PGT-A using a shared decision-making model."

The bottom line from ASRM (2024): "The value of PGT-A as a universal screening test for all patients undergoing IVF has not been demonstrated." It also notes the trials were done at experienced centers, and results at centers with less experience haven't been established.

• Fewer embryos to transfer. HFEA explains that PGT-A is a selection tool that often reduces the number of embryos available, and time to a live birth may be longer.
• Biopsy effects. ASRM says a trophectoderm biopsy showed no detectable effect on implantation in one multicenter study, but its impact "is not well understood."
• Misclassification. A euploid, aneuploid or mosaic call can be wrong; ACOG says false-positive and false-negative results are possible.
• Not a full genetic screen. ACOG says PGT has trouble detecting microdeletions and microduplications, new (de novo) variants and imprinting disorders.
• Sex is revealed. ASRM notes PGT-A can show embryo sex, which raises questions about sex selection; in the U.S., those decisions are left to patients and their providers.

• Given my age, history and expected number of embryos, what do you expect PGT-A to change for me?
• Which lab and platform do you use, and how does it report mosaic and segmental results?
• What is the clinic's written policy on transferring or storing mosaic or abnormal embryos?
• If no embryo tests euploid, what are my options?
• Will I see a genetic counselor before and after testing?
• What prenatal screening or diagnostic testing do you recommend if I conceive?

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Featured doctors: Dr. Brian Levine, a double board-certified reproductive endocrinologist and the Founding Partner and Practice Director of CCRM Fertility of New York, whose practice includes IVF, egg freezing and third-party reproduction.

• How Long Does IVF Take? Timeline Explained
• IVF Success Rates by Age: How to Read Clinic Numbers
• Egg Freezing and Age: What the Evidence Says
• Fertility Medicine Guides

• Practice Committees of ASRM and SART, "The use of preimplantation genetic testing for aneuploidy: a committee opinion," Fertil Steril 2024;122:421–34 — https://www.asrm.org/practice-guidance/practice-committee-documents/the-use-of-preimplantation-genetic-testing-for-aneuploidy-a-committee-opinion-2024/ (checked Nov. 15, 2026)
• ASRM Practice Committee, "Recurrent pregnancy loss: a committee opinion," Fertil Steril 2026;125:1023–41 — https://www.asrm.org/practice-guidance/practice-committee-documents/recurrent-pregnancy-loss-a-committee-opinion-2026/ (checked Nov. 15, 2026)
• Practice Committees of ASRM and the Genetic Counseling Professional Group, "Clinical management of mosaic results from preimplantation genetic testing for aneuploidy of blastocysts: a committee opinion," Fertil Steril 2023;120:973–82 (PMID 37678731) — https://pubmed.ncbi.nlm.nih.gov/37678731/ (record checked Nov. 15, 2026)
• American College of Obstetricians and Gynecologists, Committee Opinion No. 799, "Preimplantation Genetic Testing" (March 2020; reaffirmed 2025) — https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2020/03/preimplantation-genetic-testing (checked Nov. 15, 2026)
• Human Fertilisation and Embryology Authority (UK), "Pre-implantation genetic testing for aneuploidy (PGT-A)," treatment add-on ratings — https://www.hfea.gov.uk/treatments/treatment-add-ons/pre-implantation-genetic-testing-for-aneuploidy-pgt-a/ (checked Nov. 15, 2026)

This guide is general information, not medical advice. Talk to a licensed physician about your own fertility care.