The proper placenta's structure and function are essential conditions to correct pregnancy's and labour's course. Nowadays the role of epigenetics in this organ is more carefully investigated. Some of epigenetics' modifications as DNA methylation, non-coding RNA action or histone modification are able to change the genes' expression without the change of DNA sequence. This phenomenon is particularly intensified in the placenta. Epigenetics placenta's irregularities can be responsible for many pregnancy pathologies, for example spontaneous miscarriage, pre-eclampsia or intrauterine growth retardation, and for many postnatal diseases, such as cancer or mental problems. In the future the monitoring of epigenetics placenta's modifications enables the estimation of pregnancy complications and postnatal diseases risk. Moreover, it will be possible to understand the role of epigenetics in functions the different kinds of cells, including cancer cells.