P-105 The influence of low-lactate culture medium on IVF success rates

Study question

Could differences in lactate concentration in culture medium influence reproductive outcomes?

Summary answer

Embryos cultured in low lactate medium showed a significantly improved fertilization and blastocyst utilization rate compared to embryos cultured in high lactate culture medium.

What is known already

Lactate plays a pivotal role in embryo metabolism, particularly during early developmental stages. It serves as an essential energy substrate, complementing pyruvate and glucose, to fuel cellular processes. Beyond its role in energy production, lactate contributes to maintaining pH stability and redox balance within the culture environment. Excessive or insufficient lactate concentrations can disrupt metabolic homeostasis, leading to suboptimal embryo development.

Recent research has focused on the potential benefits of culturing embryos in low-lactate culture medium. These studies suggest that reducing lactate concentrations may alleviate oxidative stress and improve mitochondrial efficiency, thereby enhancing the overall quality of oocytes and embryos.

Study design, size, duration

An observational prospective split-sibling study was performed in a private IVF clinic between Januay and April 2024. 68 cycles, including autologous and frozen egg donation were included, with a minimum of 6 mature oocytes (MII) in autologous and 8 MII warmed in egg donation cycles. Intracytoplasmic sperm injection (ICSI) was performed. Oocytes were cultured in two different culture media and all high quality blastocysts were vitrified. In addition, 140 single frozen blastocyst transfers were performed.

Participants/materials, setting, methods

MII oocytes (n = 594) were inseminated by ICSI and then split into either high lactate G-TL (n = 297) or low lactate CSCM-NXC (n = 297) and incubated in time-lapse under the same conditions. Fertilization, blastocyst per 2PN and blastocyst per MII rates were compared.

Furthermore, 140 single frozen blastocyst transfers were performed (high lactate culture, n = 54 and low lactate culture, n = 86). Clinical pregnancy, miscarriage and ongoing pregnancy rates were compared. Chi-square analysis was used to determine significance.

Main results and the role of chance

A significant difference was observed in the fertilization rate between high lactate and low lactate embryo culture medium (72,4% and 81,8%, respectively) (p < 0,05). There was no significance in the decreased blastocyst utilization rate per 2PN observed in high lactate versus low lactate (49,3% and 56,8%, respectively). A significant difference was observed in the blastocyst utilization rate per MII in the high lactate and low lactate media (35,7% and 46,5%, respectively) (p < 0,05).

The increases observed in clinical pregnancy rate from high lactate to low lactate embryo culture (46,3% and 57%, respectively) and ongoing pregnancy rate (31,5% and 50%, respectively) are not statistically significant. There is a significant difference in the miscarriage rate, with 32% in the high lactate and 12,2% in the low lactate media, (p < 0,05).

Limitations, reasons for caution

Though the sample size exhibits statistical significance, a larger sample population could further validate the results. Additionally, more robust research into the method of action of reducing lactate in embryo culture would be valuable in fully understanding the implications.

Wider implications of the findings

Currently, blastulation success is measured per 2PN. With low lactate obtaining more blastocysts per MII, we could consider blastulation success based on the number of oocytes collected, potentially affecting patient education and expectation. At the clinical outcome level, the decrease in the rate of spontaneous miscarriage is another great advantage.

Trial registration number

No