Mosaic embryos result in equivalent live birth rates when compared to euploid embryos following frozen embryo transfer

Purpose: To compare live birth rates (LBRs) between mosaic and euploid embryos. Methods: Retrospective cohort study analyzing frozen mosaic (56) and euploid (819) embryos tested with next generation sequencing, transferred between October 2018 and December 2023. The primary outcome was LBR per embryo transferred. Secondary outcomes included LBR per embryo transfer cycle, implantation rate (IR), miscarriage rate (MR), double embryo transfer (DET) rate, twin rate, high-level (HL) versus low-level (LL) mosaicism, segmental or whole chromosomal mosaicism, freeze day and grade, and neonatal outcomes. Chi-squared and student t-test were applied, with significance set at p < 0.01. Results: Per embryo, mosaic and euploid embryos had similar LBR (50.0% versus 51.8%, p = 0.80) and IR (55% versus 56%, p = 0.88). Per cycle, biochemical pregnancy (22.0% versus 17.8%, p = 0.41), clinical pregnancy rate (53.1% versus 56.2%, p = 0.77), and MR (7.7% versus 7.6%, p = 1.00) were not significantly different. LBR in LL versus HL mosaics was 59.4% versus 37.5% (p = 0.18) and 48% versus 50% for segmental versus whole chromosomal defects (p = 1.00). Mosaic embryos were transferred in significantly older patients (37.5 vs 36.1 years, p = 0.01), but age did not affect LBR after adjustment at the time of embryo transfer (p = 0.65). DET was more frequent with mosaic than euploid embryos (41% versus 4.8%, p < 0.001), yielding a higher twin LBR (21% versus 2.7%, p < 0.001). Conclusion: Mosaic embryos had nearly identical LBR and MR to euploid embryos, supporting transfer before repeating IVF retrieval. Given the elevated twin risk with mosaic DET, single embryo transfer should be prioritized for all tested embryos.