The aims of this literature review are: to depict the main oral diseases that are related to pregnancy; to clarify some of the possible systemic mechanisms that are associated with these changes; and to address issues about oral care during pregnancy. A woman's organs undergo various physiological, neurological, and hormonal changes during pregnancy. Such changes occur gradually and are essential for the development of the fetus, providing what is needed for tissue formation and establishment of reserves for uterine and fetal life. In turn, the oral cavity shows some events during this period. Among the changes most frequently cited in the literature are pyogenic granuloma, gingivitis, and periodontitis. The inflammation of the periodontal tissues due to the formation of the biofilm increases dramatically in size and severity during the course of a normal pregnancy, even without changes in the amount of biofilm present. In addition, a decrease in salivary pH is observed in pregnant women and may lead to an increased incidence of dental caries in this period.