Genomic imprinting is an epigenetic marking mechanism by which certain genes become repressed on one of the two parental alleles. Imprinting plays important roles in mammalian development, and in humans its deregulation may result in disease and carcinogenesis. During different medical, technological and scientific interventions, pre-implantation embryos and cells are taken from their natural environment and subjected to culture in artificial media. Studies in the mouse demonstrate that environmental stress, such as in vitro culture, can affect the somatic maintenance of epigenetic marks at imprinted loci. These effects are associated with aberrant growth and morphology at fetal and perinatal stages of development.