Culture media age does not affect IVF outcomes

STUDY QUESTION: Does the storage duration of a single-step embryo culture medium within its labelled 1-year shelf-life affect embryo development, pregnancy outcomes, or birthweight in IVF? SUMMARY ANSWER: The age of a single-step embryo culture medium with a 1-year shelf-life is not associated with embryo development, cumulative live birth, or neonatal outcomes such as birthweight or preterm birth. WHAT IS KNOWN ALREADY: Media composition, pH, and osmolality are recognized as important measures of media quality. In contrast, the shelf-life of culture media is poorly studied, resulting in different expiries among suppliers, with most between 120 days and 26 weeks. These differences have far-reaching implications, with the potential to affect success rates while increasing cost and waste. Most importantly, it is critical to know if 'old' media results in similar or worse IVF outcomes than 'fresh' media. STUDY DESIGN, SIZE, DURATION: A retrospective multicentre study was conducted using 9680 IVF/ICSI cycles from 6330 patients across eight clinics in Australia between October 2020 and December 2023. PARTICIPANTS/MATERIALS, SETTING, METHODS: Inclusion criteria were autologous cycles with ≥1 fertilized oocyte and known media production date. Cycles using thawed oocytes/embryos or non-standard transfer days were excluded. All embryos were cultured in time-lapse incubators using single-step media. Cycle outcomes, including embryo development, cumulative pregnancy, live birth, preterm birth, and birthweight for singleton, were analysed using unadjusted and adjusted regression models, as well as generalized estimating equation models to account for repeated measures within same patients. MAIN RESULTS AND THE ROLE OF CHANCE: Media age at use ranged from 38 to 365 days (mean ± SD: 190 ± 61 days). No statistically significant associations were observed between media age and embryo development outcomes, including percentage of Day 5/6 blastocysts (P = 0.389) and Day 5/6 usable blastocysts (P = 0.255). Similarly, media age was not associated with cumulative cycle outcomes including clinical pregnancy (P = 0.669), ongoing pregnancy (P = 0.986), or live birth (P = 0.257) in adjusted models. Subgroup analyses, including preimplantation genetic testing cycles and fresh transfers, yielded consistent results. Among 1070 singleton live births, media age was not associated with preterm birth (P = 0.818) or birthweight (P = 0.161). LIMITATIONS, REASONS FOR CAUTION: This was a retrospective study based on a single medium type; results may not generalize to other formulations. Post-opening media handling was not captured, which may introduce unmeasured variability. Prospective studies are needed to confirm these findings across diverse media types and settings. WIDER IMPLICATIONS OF THE FINDINGS: These results support more flexible use of culture media up to expiration and suggest longer shelf-life media can be used to reduce waste and logistical burdens. Broader application could support sustainability goals in IVF practice. STUDY FUNDING/COMPETING INTEREST(S): No funding was attached to this study. D.M. has received consulting fees from Dawn-bio, Fujifilm Irvine Scientific and Overture Life; and speaker's fees from Genea Biomedx and Organon. The other authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.