Can an Abnormal Embryo Be Transferred? How Are PGT-A Results Evaluated?

In IVF treatment, receiving an “abnormal” genetic test result for an embryo can be worrying for couples. Especially when no chromosomally normal embryo is available, there may be uncertainty about how to continue treatment. However, not every embryo reported as abnormal on PGT-A has the same characteristics.

Changes affecting an entire chromosome, mosaic results and segmental changes involving only part of a chromosome should be evaluated differently. Studies reporting live births in selected cases of segmental aneuploidy highlight the importance of this distinction. However, these findings do not mean that all embryos with an abnormal result can be transferred.[1,2]

What Does an Abnormal PGT-A Result Mean?

PGT-A is a test that examines chromosome copy number in a limited number of cells taken from the embryo. The sample is taken from the outer cell layer of the blastocyst-stage embryo, which will later contribute to the placenta. Therefore, the result does not mean that every cell of the embryo has been examined individually.

Looking only at the words “normal” or “abnormal” in the report is not enough. The type of change detected and the laboratory’s reporting criteria should also be considered. You can find details on the scope of the test in our article Preimplantation Genetic Testing: PGT and Advanced PGT on our website.

What Is the Difference Between Euploid, Aneuploid and Mosaic Embryos?

The terms in PGT-A reports describe different findings:

Segmental change and mosaicism are not the same thing. Depending on the laboratory’s assessment, a segmental finding may be reported as mosaic or non-mosaic.[2,3]

What Are Segmental Deletions and Duplications?

A segmental deletion refers to the loss of genetic material in a specific part of a chromosome, while a duplication refers to an extra copy of a specific segment.

The significance of these findings does not depend only on the size of the change. The affected region and the genes it contains also matter. A “small” change is not necessarily insignificant or safe. For this reason, segmental findings require evaluation by a medical geneticist.

Can Embryos with Segmental Aneuploidy Lead to a Live Birth?

Yes. Some studies have reported live births after the transfer of embryos reported as segmental aneuploid on PGT-A.

A study published in 2024 evaluated the transfer of 25 embryos reported as non-mosaic segmental aneuploid and found a live birth rate of 24% in this group. However, the study is small and based on a retrospective analysis. In addition, prenatal genetic diagnosis was not performed in all pregnancies.[2]

A multicenter study published in 2026 also reported a live birth rate of 17.1% in 82 embryo transfers with a non-mosaic segmental aneuploidy result. This finding supports the view that some embryos reported as segmental aneuploid may retain the potential for live birth.[1]

The rates in both studies should not be interpreted directly as any individual couple’s chance of success. Patient groups, embryo characteristics and assessment methods may differ.

These results do not show that every segmental finding can be safely transferred or that a healthy birth is guaranteed. The transfer decision should be made individually, based on the characteristics of the detected change and genetic counseling.

Can a Mosaic Embryo Be Transferred?

In suitable cases, embryos with a mosaic result may be considered as a transfer option. However, the mosaicism percentage in the report should not be interpreted as the proportion of affected cells in the future baby.

Some studies have reported lower implantation rates and higher pregnancy loss rates after mosaic embryo transfers compared with euploid embryos. Before a decision is made, genetic counseling should be provided and possible outcomes and uncertainties should be shared with the couple.[3]

What Are the Next Steps If No Euploid Embryo Is Available?

If a suitable euploid embryo is available for transfer, it is usually given priority. When there is no euploid embryo, the existing reports, previous treatments and the likelihood of obtaining embryos in a new treatment cycle are considered together.

Suitable mosaic embryos and some selected segmental aneuploidy results may be evaluated individually. However, this should not be seen as an automatic “euploid–mosaic–segmental” transfer order that applies to everyone. Evidence is particularly limited for non-mosaic segmental findings.[1–3]

What Should Be Considered Before Deciding to Discard an Embryo?

Before making an irreversible decision, it is important for the report to be reviewed jointly by the IVF physician and a medical genetics specialist. If necessary, clarification is requested from the laboratory that performed the test.

The evaluation seeks answers to the following questions:

• Does the change affect the whole chromosome or only part of it?
• Is the result mosaic or non-mosaic?
• Which chromosomal region is affected?
• What are the technical limits and reporting criteria of the test?
• What other embryos and new treatment options are available?

Re-evaluating the report does not mean the result will necessarily change. The aim is to ensure the decision is based on the details of the finding, not just on the “abnormal” label.[3,4]

Is Genetic Testing Needed During Pregnancy After Transfer?

Having PGT-A does not remove the need for genetic evaluation during pregnancy. Particularly after the transfer of an embryo with a mosaic or segmental finding, prenatal screening and diagnostic options should be discussed as part of genetic counseling.

Screening tests such as NIPT do not replace diagnostic testing. The information provided by diagnostic methods such as amniocentesis, as well as their limitations and risks, is assessed individually.[3]

PGT-A Result Evaluation in Istanbul

If your PGT-A report shows an abnormal result, it is helpful to bring the full report and your previous embryology records when discussing treatment options.

At Dr. Soner Düzgüner Clinic, you can schedule a preliminary consultation to review your current results and previous treatment history. For consultations and appointments, please call +90 545 440 55 45 to reach our team.

References

1. Viotti M, Madjunkova S, Besser A, et al. (2026). Multicenter assessment of outcomes after intended or nonselective transfer of whole chromosome and segmental aneuploid embryos. Fertility and Sterility. Published online: 1 September 2026.
   DOI: 10.1016/j.fertnstert.2026.08.1124
2. Besser A, Weidenbaum E, Buldo-Licciardi J, McCaffrey C, Grifo J, Blakemore J. (2024). Healthy live births achieved from embryos diagnosed as non-mosaic segmental aneuploid. Journal of Assisted Reproduction and Genetics. 41:3379–3385.
   DOI: 10.1007/s10815-024-03282-8
3. American Society for Reproductive Medicine — ASRM (2023). Clinical management of mosaic results from preimplantation genetic testing for aneuploidy of blastocysts: a committee opinion. Fertility and Sterility. 120:973–982.
   ASRM committee opinion
4. American Society for Reproductive Medicine — ASRM (2024). The use of preimplantation genetic testing for aneuploidy: a committee opinion.
   ASRM committee opinion