Improving Embryo Culture Conditions by Reducing Oxygen Tension May Help Increase the Implantation Potential of an Embryo in the Donor Recipient Population

Abstract

Background: It has been suggested that a low oxygen environment that mimics physiological conditions may improve embryo viability and increase clinical outcomes. Utilizing 5% O2 in the embryology lab may improve culture conditions by optimizing culture media and reducing stress to the embryo. Objective: The objective of this retrospective analysis was to compare the blastocyst formation, clinical pregnancy, and implantation rates of embryos derived from donor oocytes before and after the implementation of low oxygen culture conditions. Materials and Methods: 124 donor recipients undergoing a D5 ET whose embryos were cultured in 5% CO2 and 20% O2 from Jan 2006 to July2007 were compared with a group of 29 donor recipients whose embryos were cultured in 5% O2/5% CO2/90% N2 after the implementation of low oxygen culture conditions in August 2007. All embryos were cultured in Sage Cleavage Medium from D1 to D3 and transfered to InVitroCare Blastocyst culture medium from D3 to D6. One or two embryos were chosen for transfer on D5. Results: No difference was seen in donor age, number of oocytes retrieved, or number of embryos available for culture to the blastocyts stage. There was a slight increase in blastocyst formation rates and a notable increase in CPR and implantation rates.Tabled 1nAvge. oocytesAvge. embryosAvge. ETBlast formationCPRIR5% CO2/20% O212422.915.11.855%75%67%5% O2/5% CO2/90% N22922.414.91.661%86%81% Open table in a new tab Conclusions: Although there is a difference in the two groups regarding the blast formation rate, CPR, and IR, a larger sample size is needed to show statistical significance. In our efforts to reduce the number of embryos being transfered, adjustments in the culture conditions may help improve the implantation potential of an embryo. Although the gas phase is one of many important aspects in embryo development and viability, our analysis has shown that reducing the oxygen tension enhanced culture conditions, which could have led to the increase in implantation rates and clinical outcomes.