Purpose: Pregnancy is a period in a woman’s life which has important consequences on oral health, particularly for gingival health. The present study aimed to evaluate the way in which periodontal disease (gingivitis and periodontitis) evolves during pregnancy and to identify women at higher risk of developing gingivitis and periodontitis during late pregnancy.Methods: A prospective cohort study was conducted in southern Spain, with 147 pregnant women who were assessed during the first and third trimesters of gestation in a public hospital. Data regarding gingival and periodontal health, oral hygiene and overall health status (obesity and diabetes mellitus) were collected. Reporting followed STROBE checklist.Results: A significantly higher number of women had periodontal and gingival disease in the third trimester of gestation compared with in early pregnancy. In the third trimester of gestation, 42 (28.6%) and 63 (42.9%) of women presented symptoms of periodontal disease and gingival disease, respectively. Obesity (OR: 2.834; 95%CI 0.919-8.741), worse oral hygiene during the first trimester of gestation (OR: 4.031; 95%CI: 2.12-7.65) and periodontal disease during early pregnancy (OR: 15.104; 95%CI: 3.60-63.36) most effectively predicted periodontal disease during late pregnancy.Conclusions: Pregnancy is associated with exacerbated periodontal and gingival disease symptoms throughout the different trimesters of gestation. Obesity and oral hygiene during early pregnancy were the risk factors that most contributed to the aforementioned changes in periodontal disease.