Effect of pre-IVF incubation in maturation medium on oocyte maturity, fertilization, embryonic development, and clinical outcomes following embryo transfer

Objective: Collected human cumulus-oocyte complexes (COCs) are usually inseminated after 4 to 6 hours in in vitro fertilization (IVF) laboratories. The purpose of this study was to determine the effect of short-term pre-IVF incubation in culture medium on subsequent oocyte maturation, fertilization, and embryonic development, as well as clinical outcomes. Methods: Sixty patients were divided randomly into 2 groups, pre-IVF incubation for 5 hours: 1) with (+) the designed oocyte maturation medium; 2) without (−) the designed oocyte maturation medium (transferred directly to fertilization medium for 5 hours before insemination). Oocyte maturation and fertilization were assessed, and the rate of cleavage and good quality embryos were evaluated between the 2 groups on days 2 and 3, respectively. Blastocyst development was based on the remaining number of embryos on day 3, continuously cultured to day 5 after embryo transfer or frozen on day 3, and was compared between the 2 groups. Clinical pregnancy, implantation, and miscarriage rates were also compared. Results: Oocyte maturation rates did not differ between groups (85.8 ± 14.1% vs. 90.7 ± 9.1%). However, the range of oocyte maturation rates (58.3%–100.0%) for each patient was significantly higher in the (−) group than in the (+) pre-incubation group (71.4%–100.0%). There were no differences in fertilization rates (89.9 ± 10.0% vs. 86.5 ± 12.2%) and good quality embryos (70.8 ± 19.1% vs. 62.1 ± 23.7%) between groups; however, the blastocyst development rates were significantly different between groups (73.1 ± 20.1% vs. 58.8 ± 18.2%, P <0.05). Nevertheless, clinical pregnancy (62.5% vs. 61.1%) and implantation (46.9% vs. 47.2%) rates did not differ between groups. Conclusions: These results indicate that a short pre-IVF incubation time in the designed culture medium promotes oocyte maturation and embryonic development, suggesting that short pre-IVF incubation of COCs in the designed culture medium may be important for subsequent final oocyte maturation and early embryonic development.