P-776 Impact of a poor-quality euploid blastocyst on the implantation of a good-quality one in double embryo transfers

Abstract Study question Does the transfer of a poor-quality blastocyst along with good-quality improve clinical outcomes compared to single in euploid-only cycles? Summary answer Transferring improved pregnancy rates but live birth were not significantly increased transfer. What is known already Single embryo transfers (SET) are often preferred when using euploid blastocysts good morphological characteristics. However, co-transfer poor characteristics still practiced. Studies on embryos unknown ploidy status suggested that may hinder transferred together. Controversial results imply associated similar and increases multiple rates. Outcomes such double (DET) SETs yet be determined transfers. design, size, duration Retrospective cohort two centers including 500 718 DETs only FET autologous cycles between March 2017 January 2021. Transferred graded ≥BL3CC (Gardner criteria) underwent trophectoderm biopsy days 5-7 for aneuploidy testing Next Generation Sequencing. Classification quality (good vs poor) was based inner cell mass, grades, day biopsy. Participants/materials, setting, methods Patients SET or DET euploid-blastocysts. Endometrial preparation frozen achieved hormonal replacement within natural cycle. Reported included (CP), (LB), high-order For comparison expected observed LB rates, theoretical estimated Monte-Carlo simulations binomial density function data, under assumption independency success individual embryos. Main role chance After adjusting Age, AMH, BMI, cycle method (artificial natural), higher CP (73.1% 63.8%, OR: 1.67, 95% CI: 1.12-2.55, P = 0.014). confounders, (56.8% 52.8%, 1.25, 0.87-1.83, 0.234). Moreover, group (40.4% 1.1%, < 0.001). Using model we should if co-transferred independent. The showed lower than average (observed 56.8% 66.4% [95% 59.0 73.8%], 0.0154). Limitations, reasons caution This study has retrospective estimates susceptible residual confounding from unobserved unaccounted variables. Theoretical Wider implications findings Despite CP, did increase multiple-pregnancy Lower detrimental cumulative-LB, sequential-SET preferable, regardless blastocysts. Trial registration number Not applicable