The maternal epigenome as a window into the in utero environment that the foetus experiences

Maternal stress pre-pregnancy and exposure to stress in utero has life-long negative consequences for the developing foetus. There is growing evidence that this passes through changes in foetal epigenetic markers such as DNA methylation. We hypothesize that the mother's prior life experience and changes in her external environment will change the in utero environment she provides to the developing foetus, and both will be reflected in changes to the mother's epigenome. As classical dogma states that during embryo all DNA methylation marks are removed and replaced de novo, this raises the question as to how to assess the in utero environment, examining the role it plays in the transmission of environmental cues. We suggest that the maternal epigenome can act as a proxy for the developmental environment she provided to her offspring in utero; this developmental environment determines the child's epigenome and lifelong health trajectory. Furthermore, we suggest that the maternal origin of the placental decidua make this the perfect sample for assessing the in utero environment in the context of the mothers' prior life experience, mediating maternal exposure to infant phenotype.