Purpose The influence of culture media used during in vitro fertilization (IVF) on offspring phenotype remains controversial. However, specific effects of short exposure time after fertilization remain underexplored. By evaluating Ca 2+ oscillations as a readout of the first response of eggs to their microenvironment, we aim to investigate if early differences correlate with later adult phenotypes. Methods Oocytes fertilized by ICSI were cultured for 4 h in three different media (Cook and Vitrolife, used in human IVF, and KSOM, used for mouse embryos). They were either measured for Ca 2+ oscillations or transferred into pseudo‐pregnant females. After birth, growth curves of pups were measured up to adulthood and various organs were weighed. Results Culture media significantly modulate Ca 2+ oscillations during oocyte activation. ICSI‐fertilized oocytes cultured in Cook and Vitrolife exhibited fewer oscillations, lower frequency, and reduced variability compared to KSOM. These early differences correlated with long‐term developmental outcomes: females from Cook and Vitrolife cultures were heavier throughout growth and had larger adult organ sizes compared to those from KSOM. Conclusions Brief exposure to media immediately after ICSI shapes Ca 2+ dynamics and adult phenotypes. Optimizing embryo culture protocols in assisted reproductive technologies may improve IVF outcomes by modulating metabolic pathways linked to development.