Beneficial Effect of Reduced Oxygen Concentration with Transfer of Blastocysts in IVF Patients Older Than 40 Years Old (In Vitro Fertilization) (Report‪)‬

1. INTRODUCTION Embryos from several mammal species, including human, were exposed in vivo to low oxygen concentrations, ranging from 2 to 8% observed in atmospheric air [1-3]. This probably corresponds to an adaptation mechanism, as it is proven that higher oxygen concentrations may be harmful to the embryo [4] by generating reactive oxygen species (ROS) [5-7].