The effect of oxygen concentration on preimplantation embryo development and pregnancy rate

The zygote in the female reproductive tract of human is under 5% O2 concentration. On the other hand, the embryos of infertile couples formed via the microenjection method may be subjected to atmospheric oxygen level. Oxygen controlled incubators are derived in order to decrease the possible negative effects of it.The infertile couples with the desire of having a child were included to this study. The embryos obtained were assigned to 5% and 20% O2 concentrated incubators randomly way. The embryos were controlled on the first, third and in some cases fifth days fallowing the microinjection procedure and the results were recorded. Number of fertilized oocytes, number of blastomeres on the third day, fragmentation on the third day, number of good quality embryos on the third day, compaction on the third day, blastocyst formation on the fifth day, good quality ICM formation on the fifth day, good quality trophoblast formation on the fifth day, implantation and pregnancy rates were compared according to Mann-Whitney U test. Compaction rate in the third day, blastocyst formation rate in the fifth day and good quality ICM formation in the fifth day were statistically significantly higher in 5% O2 concentration group (p<0.005). This significance was high for good quality ICM formation on the fifth day. There was no difference for other parameters. The implantation rate was slightly higher in the 5% O2 group, but this difference was not statistically significant.Those findings show that the embryos obtained in 5% O2 concentration group had better qualities, being significant especially in the morula and blastocyst stages, but this did not have any effect on the pregnancy and implantation outcomes. However further studies should be designed in order to investigate the long term effects of this difference in the qualities.