Evaluation the effect of lowered incubator oxygen tension on embryo quality

OBJECTIVE: Using sibling human oocytes, a prospective study was carried out to analyze the effect of 5% (environment) and 21% (atmospheric) oxygen (O2) on prolonged development of embryos.DESIGN: The outcomes measured: fertilization rate, optimal embryos and blastocysts, pregnancy and implantation rates.MATERIALS AND METHODS: This prospective study started in January, 2010, included 63 assisted reproduction cycles in which women were 35 ± 4,8 years old,. Embryos of patients were randomly assigned for culture in either a 21% O2 or 5% O2. Based on day five morphology, embryos were selected for transfer, and three different transfer's sets were established: only embryos derived from low oxygen incubator group; at least one embryo derived from low oxygen incubator group and only embryos derived from high oxygen incubator group.RESULTS: A total of 117 embryos were selected for transfer. We did not find any difference between the mean number of embryos selected for transfer from cultured on atmospheric or environment oxygen (0.8 ± 1.0 versus 1.1 ± 1.0). Embryos cultured in a 5% O2 did not resulted in higher rate of implantation (27.2% versus 31.6%), but a higher pregnancy rate (45.4% versus 40.0%) when compared with rates among women whose embryos were cultured in an atmospheric O2.CONCLUSION: The potentially damaging effect of free O2 radicals to cultured embryos may be reduced by adding scavengers to the culture media or by reducing the incubator O2 levels. It is suggested that is the inner cell mass (ICM) of the blastocyst that is preferentially damaged when cultured in supraphysiological O2 concentrations. Our results showed a higher pregnancy rate when embryos were cultured on 5% O2. We could argue that these are preliminary results and more studies are been developed in order to evaluate the efficiency of environment culture. OBJECTIVE: Using sibling human oocytes, a prospective study was carried out to analyze the effect of 5% (environment) and 21% (atmospheric) oxygen (O2) on prolonged development of embryos. DESIGN: The outcomes measured: fertilization rate, optimal embryos and blastocysts, pregnancy and implantation rates. MATERIALS AND METHODS: This prospective study started in January, 2010, included 63 assisted reproduction cycles in which women were 35 ± 4,8 years old,. Embryos of patients were randomly assigned for culture in either a 21% O2 or 5% O2. Based on day five morphology, embryos were selected for transfer, and three different transfer's sets were established: only embryos derived from low oxygen incubator group; at least one embryo derived from low oxygen incubator group and only embryos derived from high oxygen incubator group. RESULTS: A total of 117 embryos were selected for transfer. We did not find any difference between the mean number of embryos selected for transfer from cultured on atmospheric or environment oxygen (0.8 ± 1.0 versus 1.1 ± 1.0). Embryos cultured in a 5% O2 did not resulted in higher rate of implantation (27.2% versus 31.6%), but a higher pregnancy rate (45.4% versus 40.0%) when compared with rates among women whose embryos were cultured in an atmospheric O2. CONCLUSION: The potentially damaging effect of free O2 radicals to cultured embryos may be reduced by adding scavengers to the culture media or by reducing the incubator O2 levels. It is suggested that is the inner cell mass (ICM) of the blastocyst that is preferentially damaged when cultured in supraphysiological O2 concentrations. Our results showed a higher pregnancy rate when embryos were cultured on 5% O2. We could argue that these are preliminary results and more studies are been developed in order to evaluate the efficiency of environment culture.