ABSTRACT: With the increasing use of Assisted Reproductive Technologies (ART) for treatment of human infertility, there is an increasing requirement for embryo culture conditions that perform as similar to nature as possible. How good the match, however, cannot be tested experimentally in human. We solved the central question of how well ART culture protocols prepare embryos for postimplantation development, under the provisions of the 'mouse embryo assay' (MEA). Our side-by-side comparison of 8 conditions [i.e., 3 culture conditions (KSOM, HTF and ISDM1) plus the in vivo system in two different mouse strains (B6 and CD1)] shows that mouse embryos cultured under ART conditions are differentially primed for postimplantation development, and that certain ART protocols outperform the oviduct. The distinct performances of blastocysts formed in ART vs. oviduct do not correlate with any significant transcriptome changes, whereas protein analysis by immunoconfocal microscopy reveals differences in the allocation of embryonic cells to the three germ layers of blastocysts. We conclude that in vitro technology is not always a defective copy of nature, and that the choice of ART protocol primes the embryos for subsequent development. 22 samples were analyzed. B6KSOM: Mouse B6 background, E3.5 blastocysts in KSOM medium, 3 biological rep B6HTF: Mouse B6 background, E3.5 blastocysts in HTF medium, 3 biological rep B6ISM1: Mouse B6 background, E3.5 blastocysts in ISM1 medium, 3 biological rep B6vivo: Mouse B6 background, E3.5 blastocysts in vivo, 3 biological rep CD1KSOM: Mouse CD1 background, E3.5 blastocysts in KSOM medium, 1 biological rep CD1HTF: Mouse CD1 background, E3.5 blastocysts in HTF medium, 3 biological rep CD1ISM1: Mouse CD1 background, E3.5 blastocysts in ISM1 medium, 3 biological rep CD1vivo: Mouse CD1 background, E3.5 blastocysts in vivo, 3 biological rep