#146 : Low-Lactate Culture Medium Increases the Percentage of Usable Blastocysts from Advanced Maternal Age Patients: A Sibling-Oocyte, Monocentric Study

Background and Aims: Excess lactate in culture medium accumulates may adversely affect the embryo as metabolic stress. The purpose of this study is to investigate whether culture media with a low-lactate concentration have an effect on embryonic development in IVF. Method: A split sibling study was performed on 8313 oocytes from 1,312 ICSI cycles from which at least two matured oocytes were retrieved from January 2020 through August 2022. Sperm-injected oocytes were allocated to Continuous Single Culture-NX (NX, N=4352) which contains a low concentration of lactate (1mM) and Global Ⓡ total Ⓡ LP (GL, N=3961), which contains 5mM concentration of lactate. Patients were classified into subgroups of <40 years (854 cycles) and [Formula: see text]40 years (458 cycles). Single frozen embryo transfers were performed in 859 cycles (NX; N = 500, GL; N = 359). Embryo development up to Day 6, clinical pregnancy and miscarriage rates were compared. Usable blastocysts were defined as any blastocyst cryopreserved on day 5 or day 6. P<0.05 was considered statistically significant. Results: The mean patient age was 37.1 ± 4.4 years. Overall fertilization rates and the blastocyst development rate were significantly higher in NX than GL (80.7% vs. 78.9% and 62.3% vs. 59.8% respectively). There was no significant difference in blastocyst utilization rate on day 5 with all ages considered (36.2% NX vs. 34.2% GL). There was no significant difference in blastocyst development rate for patients [Formula: see text]40 years, but for patients [Formula: see text]40 years, blastocyst development rate and day 5 usable blastocyst rate were significantly increased in NX (51.2% vs. 46.4% and 26.2% vs. 22.4% respectively). There were no significant differences in the clinical pregnancy or miscarriage rates (48.8% vs. 49.9% and 22.1% vs. 21.8% respectively). Conclusion: Our results suggest that the lower concentration of lactate in culture medium is effective for late embryonic development in advanced maternal age patients.