Is Fertilization Rate Affected by Type of Culture Media Used Post-Insemination?

Abstract

Background: Culture media for IVF and embryo growth has evolved from simple salt solutions to sequential media designed to mimic the in vivo milieu at different developmental stages. While fertilization is optimized with glucose-rich media, penetration of the oocyte occurs within 3 hours. Minimal coincubation, the process of removing oocytes from the media containing high concentrations of sperm and granulosa cells after 3 hours is a common lab practice to reduce the influence of a high glucose concentration and waste produced by the other cells in the culture system of sperm and oocytes. We have previously demonstrated that moving oocytes after sperm injection (ICSI) to cleavage stage media (G1) did not affect fertilization rate, embryo growth or pregnancy rate (Hammitt et al., 2000). However, IVF oocytes remain in fertilization media (HTF) until after fertilization is confirmed. Objective: Our study was designed to assess if G1 media affects fertilization rate or zygote morphology. Materials and Methods: IRB-approved retrospective chart review. Between June 2001 and December 2004, a quality improvement evaluation was performed to assess the effect of culture in G1 vs HTF after a 3 hour co-incubation period at time of insemination. Only patients with a large cohort of oocytes were included, and between 2 to 6 oocytes were cultured in G1 post-insemination until fertilization check. Fertilization rate was recorded as the endpoint and compared between G1 and HTF groups. Mean grade of fertilized oocytes, where 0 equals the highest quality, and percentage of poor quality pronuclear embryos were also evaluated. Results: Type of media did not affect fertilization rate or pronuclear grade. Please see table for details.HTF vs. G1 MediaG1HTFFertilization rate % (mean)70 ± 1869 ± 18Pronuclear grade (mean)0.87 ± 0.540.75 ± 0.37Poor pronuclear grade41/163 (25%)153-591 (26%) Open table in a new tab Conclusions: These results demonstrate that fertilization rates and early embryo development are not compromised by oocyte placement into G1 media 3 hours following co-incubation in HTF media. G1 media may supply a more physiological environment for early embryo development and provide additional long-term benefits to be investigated in future studies.