Triple gas versus 5% carbon dioxide (CO2): A study on development of embryos in triple gas incubators, triple gas dessicators and CO2 incubators.

Abstract

Objective: The purpose of this study was to ascertain the influence of two different gas phases on pregnancy outcome in an ART program. Design: Retrospective study. Materials/Methods: This study was carried out on 483 consecutive cycles from January, 2000 to February 15, 2001. For this study, only patients under 39 years of age were selected. They were allocated to either a single gas incubator (5.4% CO2 in air), 5.4% CO2, 5% O2 in nitrogen incubator or a dessicator purged with triple gas mixture (inside a 5% CO2 incubator). P1, Blastocyst medium and synthetic serum substitute (all from Irvine Scientific) were used for culture in microdrops under oil. Insemination of oocytes was done either with IVF method or with ICSI. Fertilization, cleavage and pregnancy rates were calculated. All embryo transfers were performed on day 3 (8 cell stage embryos). Statistical analysis was performed using two-way ANOVA and chi-square test as indicated with p < 0.05 considered statistically significant. Results: Comparison of these three groups showed no statistical difference in fertilization, cleavage or pregnancy rate. Results are presented in the following table. Influence of gas phase on fertilization, cleavage and pregnancy rates. Tabled 15% CO2 incubatorTriple gas incubatorDessicator (triple gas)Cycles17227140Oocytes Inseminated20143442496Fertilization1425 (71%)2544 (74%)400 (81%)Cleavage (less cryo)1100 (99%)1982 (98%)296 (96%)Transferred659 (3.8/P)1125 (4.1/P)134 (3.3)Pregnancy76 (44%)142 (52%)18 (45%) Open table in a new tab Conclusions: Our results with day 3 embryo transfer show no significant difference on any parameter in these two gas groups. These results are similar to previous studies on day 2 (4 cell stage) embryo transfers when these same two gas systems were compared. It seems therefore, for short time culture, i.e., 2 or 3 days, 5% CO2 is as good as triple gas mixture. However, if embryos are grown to the blastocyst stage, blastocysts under triple gas mixture grow significantly more cells than those blastocysts in the 5% CO2 in air gas phase. Consequently this might lead to higher implantation rates (ASRM: Abst-O-079, 1999).