JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):175
Poster Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263913

P-163. Mosaic Embryo Transfer: clinical outcomes and current evidence

Vanelise dos Santos de Paula¹

¹ Pontifícia Universidade Católica de Minas Gerais - PUC Minas - Belo Horizonte - MG - Brasil

Objective: To summarize the most recent evidence on the clinical outcomes associated with mosaic embryo transfer, considering implantation rates, spontaneous abortion, live birth, and implications for clinical practice in Assisted Reproduction.
Methods: A literature review was conducted using the SciELO and PubMed databases to identify articles published between 2021 and 2025 addressing mosaic embryo transfer in human reproduction treatments. Five articles were selected, including systematic reviews and meta-analyses reporting relevant data on the topic.
Results: Extended culture to the sixth or seventh day of development has been associated with increased rates of mosaicism. This observation may be explained by the tendency of embryos with delayed progression to the blastocyst stage to contain aneuploid cell populations, which can compromise developmental competence, prolong the timing of blastulation, and consequently increase the likelihood of mosaicism being identified in trophectoderm biopsy samples. Interestingly, the influence of maternal age on mosaicism differs from that observed with uniformly aneuploid embryos. While aneuploidy rates rise with increasing maternal age, mosaicism appears more frequent in embryos from younger patients (<34 years). Male factors, however, showed no significant association with mosaicism. Early-stage embryos also demonstrate an increased incidence of mosaicism compared with more advanced-stage embryos, possibly due to aneuploidy depletion — a self-correcting mechanism that eliminates or reduces the proportion of chromosomally abnormal cells during development. Technical limitations of preimplantation genetic testing for aneuploidy (PGT-A) may also contribute, as some uniformly normal or abnormal embryos may be misclassified as mosaic. Clinical outcomes of mosaic embryo transfers (METs) remain suboptimal compared with euploid embryo transfers or transfers without PGT-A. In a sample of 2,155 METs, there were 440 live births (20.42%), indicating that although implantation and healthy development are possible, the rates of clinical pregnancy and live births are lower (40.1% versus 59.0% and 27.1% versus 47.0%) and miscarriage rates are higher than with euploid embryos (33.3% versus 20.5%).
Conclusion: Mosaicism is associated with delayed embryonic development. Although mosaicembryo transfer is a viable option when no euploid embryos are available, outcomes aregenerally less favorable. Stronger prospective evidence, standardized diagnostic criteria, andindividualized clinical strategies are essential to support safe and effective practice.