In this clinical randomized trial, 158 patients will be included of which half of the fertilized oocytes will be cultured individually (standard culture system) and half of the fertilized oocytes will be cultured in group in a WOW dish, both during five days of culture. The aim of this study is to increase the number of blastocysts suitable for transfer or cryopreservation by culturing the embryos in WOW dishes.