Effects of Reduced Oxygen Concentrations on IVF Outcome

Abstract

Background and Significance: Although human embryos can develop in atmospheric oxygen concentrations, it has been suggested that low oxygen concentrations mimicking physiological conditions may improve embryo viability due to a decreased production of free oxygen radicals. It has been hypothesized that mimicking physiological conditions by utilizing CO2 with 5% oxygen vs. CO2 with 20% oxygen (atmospheric conditions) will improve the development of the embryo in vitro resulting in increased fertilization rates and pregnancy rates.Objective: The objective of this study was to compare the effects of two standard oxygen concentrations, physiological (5% oxygen in dessicator) and atmospheric (20% oxygen on shelf), on fertilization, embryo development and IVF outcome with our culture system in an IRB approved study.Materials and Methods: 1045 oocytes from 106 patients were randomized by week of oocyte retrieval to either physiologic (5% O2,5%CO,90%N2) or atmospheric (5% CO2 with the balance as air) conditions for insemination (IVF or ICSI) and culture in cleavage media (Sage) under oil. The three factors compared were fertilization rates, quality of Day 3 embryos and pregnancy rate. The quality of Day 3 embryos was assessed by Mean Embryo Score (MES) which takes into account the mean number of blastomeres and grade of embryos of a single patient. Embryos determined on Day 3 to meet the criteria to proceed to Day 5, were transferred into blast media (Sage) and cultured under physiologic conditions regardless of their initial randomization.Tabled 1Day 3Day 5Group 1Group 2p-valueGroup 1Group 2p-value# of Patients3945NS1012NSAve age3938NS32.935.8NSTotal Eggs312415NS148170NSTotal 2PN188250NS115113NSFertilization Rate (%)60%60%NS78%67%NSMES21.0217.350.005722.5921.34NSPregnancy Rate (%)28%31%NS70%33%NS Open table in a new tab Conclusion: In our culture conditions, the differences in oxygen concentration did not affect the fertilization outcome or the pregnancy rate. While there was a significant difference in the MES between the physiologic and atmospheric groups on Day 3 and not on Day 5, pregnancy outcome was not affected. Larger studies may further clarify these results. Background and Significance: Although human embryos can develop in atmospheric oxygen concentrations, it has been suggested that low oxygen concentrations mimicking physiological conditions may improve embryo viability due to a decreased production of free oxygen radicals. It has been hypothesized that mimicking physiological conditions by utilizing CO2 with 5% oxygen vs. CO2 with 20% oxygen (atmospheric conditions) will improve the development of the embryo in vitro resulting in increased fertilization rates and pregnancy rates. Objective: The objective of this study was to compare the effects of two standard oxygen concentrations, physiological (5% oxygen in dessicator) and atmospheric (20% oxygen on shelf), on fertilization, embryo development and IVF outcome with our culture system in an IRB approved study. Materials and Methods: 1045 oocytes from 106 patients were randomized by week of oocyte retrieval to either physiologic (5% O2,5%CO,90%N2) or atmospheric (5% CO2 with the balance as air) conditions for insemination (IVF or ICSI) and culture in cleavage media (Sage) under oil. The three factors compared were fertilization rates, quality of Day 3 embryos and pregnancy rate. The quality of Day 3 embryos was assessed by Mean Embryo Score (MES) which takes into account the mean number of blastomeres and grade of embryos of a single patient. Embryos determined on Day 3 to meet the criteria to proceed to Day 5, were transferred into blast media (Sage) and cultured under physiologic conditions regardless of their initial randomization. Conclusion: In our culture conditions, the differences in oxygen concentration did not affect the fertilization outcome or the pregnancy rate. While there was a significant difference in the MES between the physiologic and atmospheric groups on Day 3 and not on Day 5, pregnancy outcome was not affected. Larger studies may further clarify these results.