Embryos labeled aneuploid by PGT-A lead to healthy euploid twins

A new case report describes the healthy birth of dizygotic twin girls from embryos labeled as aneuploid by PGT-A, highlighting the limitations of embryo testing and the need to reconsider strict discard protocols.

PGT-A was developed to help identify chromosomally normal embryos and improve the chances of a successful IVF pregnancy. By screening for extra or missing chromosomes, PGT-A aims to reduce the risk of miscarriage and prioritize embryos most likely to lead to a healthy live birth. But what happens when PGT-A says none of your embryos are normal?

Embryos labeled as “aneuploid” are typically not transferred and may be discarded, under the assumption that they’re incapable of producing a healthy baby.

However, there is some evidence that these aneuploid embryos may result in healthy live births. A new case report by Tise et al. (2025) adds to this evidence.

For more background reading, check my Complete guide to PGT-A.

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Case report details

The case involves a 42-year-old woman and her 49-year-old partner, who lost their daughter in an accident and pursued IVF with PGT-A to try for another girl in 2017. Two IVF cycles produced four embryos, tested by a commercial lab using NGS-based sequencing technology still in use today (Ion SingleSeq and Ion ReproSeq):

• A euploid male (graded 5AB)
• An aneuploid female (5AB, monosomy 5, monosomy 18).
• An aneuploid female (4CC, monosomy 11p).
• An aneuploid female (4CC, monosomy 7, monosomy 9, monosomy 18).

Note that the authors consistently refer to these embryos as “non-mosaic aneuploids,” indicating they were classified as fully aneuploid, and not mosaic.

At the time in 2017, the clinic’s policy allowed for the transfer of aneuploid embryos under certain conditions, including comprehensive genetic counseling and a mandatory waiting period. After thorough discussion, the couple chose to transfer all four embryos, with the three aneuploid embryos transferred as a “compassionate transfer.” Traditionally, this term refers to transferring embryos during a time in the cycle when implantation is unlikely, often as a method for discarding embryos. In this case, the term was used more broadly to describe transferring embryos with very low expected viability (the aneuploids) alongside a euploid embryo that was still expected to result in pregnancy.

Surprisingly, the patient conceived a dichorionic, diamniotic (di-di) twin pregnancy, meaning each twin had their own placenta and amniotic sac — suggesting that two separate embryos implanted and developed independently.

Both babies were delivered at 36 weeks and were confirmed to have normal female karyotypes without any chromosomal abnormalities. Based on their genetic profiles, the twins were dizygotic and appear to have come from two of the embryos labeled aneuploid — either the 5AB and 4CC or from the two 4CCs — and not from the euploid male.

Nearly seven years later, the twins are both healthy with no developmental issues.

Conclusions

So how can this happen? The authors propose several biological explanations for this result:

• Sampling error: PGT-A biopsies a few cells from the trophectoderm, which forms the placenta, not the ICM that becomes the fetus.
• Embryonic self-correction: Embryos may shed abnormal cells before implantation.
• Technical artifacts during DNA sequencing.
• Confined mosaicism: Abnormal cells may be limited to the trophectoderm, while the ICM is normal.

The authors acknowledge the low chance of success with aneuploid embryo transfers, but caution that excluding them could limit patients’ options, and they recommend re-evaluating selection and discard protocols that rely only on PGT-A. They also advise against transferring multiple embryos, even in cases of compassionate transfer, noting that the couple in this case experienced complications related to a twin pregnancy.

The same Stanford team who authored this case report was inspired by the outcome to launch the Transfer of Mosaic and Aneuploid Embryos (TAME) study. The group is actively enrolling up to 300 patients to investigate outcomes after transferring single embryos labeled as aneuploid or mosaic by PGT-A (no multiple embryo transfers). The study tracks pregnancies and follows any resulting children for up to five years, collecting medical records and developmental data to evaluate risks and long-term health. The expected primary completion date is April 2035, with full study completion projected for April 2039. You can learn more at clinicaltrials.gov/study/NCT04109846.

Here’s some additional posts you might want to check out on Remembryo:

• The problems with PGT-A: A 2025 opinion — A 2025 opinion article highlights some of the issues with PGT-A, mainly its uncertain benefit, technical flaws, high costs, and the risk of discarding potentially viable embryos.
• ASRM’s 2024 committee opinion on the use of PGT-A — The ASRM has released their 2024 committee opinion on the use of PGT-A, covering the use of PGT-A for patients with a good prognosis, advanced age, donor eggs, recurrent pregnancy loss and more.
• IVF outcomes following aneuploid embryo transfer — Researchers in a 2020 study performed a clinical trial and transferred aneuploid embryos, finding that no whole chromosome aneuploids led to a live birth, while segmental aneuploids did.
• 144 “abnormal” (aneuploid/mosaic) embryos and their outcomes — Researchers in a 2022 study reported on the outcomes of 144 “abnormal” embryos, consisting of aneuploids and mosaics, finding a single live birth with an aneuploid and more favorable results with mosaics.
• Depletion of aneuploid cells in mosaic embryos — Researchers in a 2021 study investigated “self-correction” in a stem cell-based model for mosaic embryos and found that aneuploid cells in a mosaic are more likely to change into trophectoderm cells or die, while euploid cells accumulate in the ICM.

Related studies

These additional studies were referenced by the authors of the paper and haven’t been covered on Remembryo. They may be helpful if you’re exploring this topic further. This section is available for paid subscribers.

Reference

Tise CG, Verma K, Rivera-Cruz G, Chamanara S, Gerber SK, Boyd A, Mazzoni R, Nel-Themaat L, Behr B, Milki AA, Lathi RB. Healthy euploid dizygotic twin birth after transfer of non-mosaic aneuploid embryos. Fertil Steril. 2025 Jun 25:S0015-0282(25)00538-2. doi: 10.1016/j.fertnstert.2025.06.033. Epub ahead of print. PMID: 40578663.

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.

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