Purpose To assess the impact of embryonic stem cell culture medium (ESCM) on the pre-and postimplantation development of the mouse embryo, as a mammalian model, in comparison with the conventional culture medium, a potassium simplex optimized medium (KSOM). Methods Development in ESCM versus KSOM was compared in terms of embryo morphology, cleavage, cavitation, hatching, cell number, expression of TE and ICM transcription factors (Cdx2 and Oct4, respectively), implantation, and development in utero.