Aneuploid embryo success rates after transfer are very low, with about 1–2% leading to a live birth, likely due to undetected mosaicism after PGT-A rather than true whole chromosome aneuploidy.
Chromosomal errors in meiosis/mitosis
A 2026 study suggests that restoring the protein SGO1 can reduce early chromosome separation in eggs, a process that might help reduce embryo aneuploidy, though this was not directly tested.
A 2025 case report shows that some ICSI-derived 3PN embryos can be rescued by removing the extra female pronucleus, resulting in a healthy live birth, but the technique remains experimental.
Using a new non-toxic imaging method, researchers watched living human embryos divide in real time and discovered that chromosome separation errors linked to mosaicism can arise even at the blastocyst stage, showing that mosaicism is a dynamic process rather than one confined to early development.
Researchers in a 2025 study performed PGT-A on whole embryos, including arrested embryos and different developmental stages, finding high rates of euploidy.
A 2025 study re-analyzed embryos that tested as mosaic by NGS-based PGT-A using SNP karyotyping and found that one-third of those “mosaics” were actually uniformly aneuploid.
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.
Researchers, in a 2024 study, have discovered that mutations in genes that code for specialized proteins called kinesins could lead to increased risk of aneuploidy and accelerate the aging process.
A 2024 study performed a more sensitive type of PGT-A by analyzing single cells, finding that nearly all blastocysts and fetal tissue contain some level of mosaicism.
Aneuploid embryos, with an abnormal number of chromosomes, are a major cause of miscarriages, often linked to maternal age and errors in meiosis. In this post, we’ll explore what chromosomes and aneuploidy are, how meiosis errors cause aneuploidy, and the factors contributing to these errors, including age, genetics and mitochondrial dysfunction.
Researchers in a 2023 study found that arrested embryos have a high degree of aneuploidy, which is mainly due to mitotic errors that occur after fertilization. In a separate analysis of non-arrested embryos, they found that good quality/day 5 embryos have less aneuploidies compared to poor quality/day 6 and 7 embryos.
Evidence up to 2022 shows that a single PGT-A biopsy is highly concordant (similar) with the rest of the embryo when the embryo is aneuploid or euploid, but not when it’s mosaic or segmental.
