Effect of different sibling human embryo culture volumes on clinical outcomes: a retrospective cohort study.

OBJECTIVE

Single-embryo culture has been adopted to select viable human embryos for transfer, and several modifications-including adjustments in culture medi-um volume-have been proposed to overcome its lim-itations. This study aimed to evaluate whether different culture volumes affect human embryo development and clinical outcomes.

METHODS

This retrospective cohort study included 6,173 individually cultured sibling embryos obtained from 859 normal-responder women who underwent in vitro fertilization (IVF) or intracytoplasmic sperm injec-tion between November 2018 and November 2019 at a single fertility center. The embryos were cultured indi-vidually in 30μl (n=3,271) or 10μl (n=2,902) of Syd-ney IVF medium. Embryo quality on days 2, 3, and 5, embryo utilization rates, and fresh embryo transfer out-comes were compared.

RESULTS

No significant differences were observed in embryo utilization rate (35.46 vs. 35.25%; p=0.86) or in the rates of good-quality embryos on day 2 (43.36 vs. 42.66%; p=0.18), day 3 (44.88 vs. 43.31%; p=0.22), or day 5 (18.00 vs. 18.00%; p=0.82). Among 249 fresh embryo transfers, clinical pregnancy rates (37.91 vs. 40.63%; p=0.67) and all other pregnancy-related out-comes were comparable.

CONCLUSIONS

Culture volume did not affect embryo quality, embryo utilization rate, or clinical pregnancy rates. These results suggest that varying culture vol-umes does not compromise embryonic developmental competence or clinical outcomes, thus supporting the flexible use of different culture volumes in individual em-bryo culture systems in clinical ART practice.