JBRA Assisted Reproduction 2025;29(Suppl.2 SBRA 2025):71
Oral Presentation
29^th Annual Congress of the SBRA. São Paulo/SP - Brazil, 2025
doi: 10.5935/1518-0557.20263633

P-59. Differences in Maturation Status of Oocytes Over Time in Low Versus High Lactate Embryo Culture Media

Vanessa Rosa¹, Rose Marie Roth¹, Nate Koepler¹, Chen Shan¹, Lindsey Vermilyea¹, Dara Berger¹, Spencer Richlin¹, Erin Dipietro¹

¹ Illume Fertility - United States

Objective: To evaluate how varying lactate concentrations in culture media influence the rate of oocyte maturation.
Methods: This retrospective cohort analysis compared 187 autologous ICSI cycles between January 1, 2024-April 30, 2024, to 184 autologous ICSI cycles of the same period in 2025. A vaginal oocyte retrieval (VOR) was performed for all cycles, yielding a total of 2,363 oocytes in 2024 and 2,428 oocytes in 2025. Post-retrieval oocytes were cultured in either a high lactate (HL) medium (3.9mM) or a low lactate (LL) medium (1.0mM). After 90-120 minutes, oocyte maturation was assessed by removing the surrounding cumulus cells using hyaluronidase, followed by the visualization of the first polar body. All mature metaphase II (MII), and immature, germinal vesicle (GV) and metaphase I (MI), oocytes were noted at the time of denudation. These gametes were reassessed for maturity after two hours, immediately prior to intracytoplasmic sperm injection (ICSI). The cohort was initially evaluated with t-tests to determine statistical significance. To address maternal age as a potential confounder, statistical evaluation was repeated for a subset with a restricted maternal age (less than 35 years of age) to validate overall findings.
Results: Overall, the average number of oocytes retrieved per patient was similar in both groups (2024=12.6, 2025=13.2 p=0.573). After treatment with hyaluronidase, the oocyte maturation was 77.2% in the low lactate CSCM-NXC culture media group, and 71.7% in the HL medium. (p=0.007). At the time of ICSI, 74.2% of immature oocytes from the HL group reached maturity compared to 80.1% in the LL group p=0.004). Among patients under 35 years of age, oocyte maturity was significantly higher in LL culture conditions compared to HL culture conditions at the time of denudation, (77.1% and 69.3%, p=0.045), respectively) and at the time of ICSI (78.6% and 70.6%, p=0.031), respectively. The overall rate of maturity between denudation and ICSI were similar in both culture conditions.
Conclusion: A LL concentration in culture media improves the rate of oocyte maturity when compared to media with a HL level. The data analysis demonstrates a significant improvement in the rates of nuclear maturation in all ages and in patients with a maternal age less than 35 years old when comparing HL and LL culture medium between 90-120 minutes of culture time.