The aim of the study is to review systematic cohort and randomized trials on the relationship between periodontitis and preeclampsia. Periodontitis is an independent risk factor for preeclampsia (PE), and periodontal treatment could play a significant role in the prevention of this pregnancy complication.A total of 821 items (published until March 2019), thematically related to the relationship between periodontitis, its treatment and the incidence of preeclampsia, were collected from the databases of PubMed, Scopus, Google Scholar and the Polish Database of Medical Bibliography and analyzed. In the end, 6 cohort studies and 3 randomized controlled trials (from the years 2003-2016) were deemed eligible for the review. The main exclusion criteria were as follows: case-control and cross-sectional studies, medical and dental conditions.A significant relationship between periodontitis and the risk for developing preeclampsia was demonstrated in 5 cohort trials, which was not confirmed by only 1 study. A total of 2724 pregnant women, including 195 (7.16%) with PE, were analyzed. In 3 randomized trials which assessed the impact of non-surgical treatment (scaling and root planing = SRP) on the occurrence of preeclampsia, the preventive effects of the implemented treatment was not confirmed. A total of 116 women from the group of 1825 pregnant subjects undergoing the non-surgical treatment (SRP) and 116 women from the control group of 1827 pregnant women were subsequently diagnosed with PE, which amounted to 6.30% and 6.35%, respectively.The cohort studies indicated that periodontitis may result in an increased risk for developing PE. A more detailed analysis regarding the impact of potential risk factors and modification of further studies (clarification of how periodontitis and preeclampsia should be defined in observations, consideration of disease severity, earlier at 12-16 weeks of gestation - implementation of the non-surgical treatment, modification and extension of the classical protocol of the non-surgical treatment of periodontal diseases, as well as conducting European studies), are necessary due to considerable discrepancies in the available literature sources (cohort and randomized observations).