The electrophoretical activity of nuclei (EMN) occurs in all cells of the human body. The EMN is variable and depends on the particular stage of human ontogenesis. The factors that modify the ontogenesis may influence the electrophoretical activity of nuclei. The aim of the study was to compare the index of electrophoretical activity of nuclei (index EMN) derived from the buccal epithelium of 40-week newborns (n = 26) from healthy, single pregnancies of smoking mothers with newborns (n = 31) of non-smoking mothers. The cells of the buccal epithelium were analysed using light microscope in the environment of alternating field (voltage 20-30 V; intensity 0.1 mA; frequency 1-2 Hz) generated by Biotest processor. In each group we estimated the number of cells with mobile nuclei and cells with motionless nuclei per 100 cells being observed. The result of this research was that there is not activity of nuclei in the group of newborns of smoking mothers (index EMN = 0 with p < 0.05). The absence of activity of nuclei makes it impossible to use the EMN method for estimation of biological age in the group of newborns of smoking mothers.