Objective — to identify differentially-expressed proteins and to study post-translational modifications of proteins in the placenta at placental insufficiency (PI). Material and methods. The study included 28 women, 15 of whom pregnancy was complicated by the PI, and 13 women whom pregnancy was without complications. Post-translational modifications of proteins of the placenta (amidation, amination, carbonylation) was evaluated by spectrophotometry methods. Differentially-expressed proteins were identified by using a two-dimensional electrophoresis and time-flight mass spectrometry. Results. PI is accompanied by post-translational modifications of proteins placenta. It reduces the number of amine groups, as well as easy- and strongly bound amide groups, which leads to a redistribution of hydrogen and electrostatic interactions in proteins is reduced as a result of their resistance to the influencing factors. Reverse direction changes characteristic of carbonylation rate: the level of carbonyl derivatives (oxidized amino acid residues of the protein) increases at PI. Revealed post-translational modification of proteins placenta affects their proteomic spectrum. At PI identified 8 proteins whose expression in the placenta dramatically reduced (or absent). Among these proteins are chaperones involved in the reconstruction of the correct structures of the polypeptide chain; the proteins that control the transcription processes of cellular proliferation, cytokinesis, power generation, the formation of the cytoskeleton, intra- and intercellular transport. Expression of the 4 proteins increased. Changing their products, one side, may have a negative effect on metabolic processes in placental tissue, on the other hand have a compensatory value contributing to prevention of decompensated PI. Conclusions. Formation of PI is accompanied by post-translational protein molecules damage the placenta, manifested opposite changes in the content of active functional groups, as well as the modification of the expression of multifunctional proteins that may be one of the primary links in violation of the protein balance of the placenta at this complication of pregnancy.