Periodontal disease is one of the most common chronic inflammatory disorders that affect tissues surrounding the tooth. 1 Generally, periodontal disease can be classified into two stages based on the severity: gingivitis and periodontitis. Gingivitis is a mild form characterized by inflammation of the soft tissues surrounding a tooth or the gingiva, while periodontitis is a more severe form characterized by destruction of supporting structures of the teeth including periodontal ligament, bone, cementum, and soft tissues. 2 Despite its effect on tooth-supporting tissues, periodontal disease is also suggested to have a cause-and-effect relationship with various systemic diseases, such as adverse pregnancy outcomes. 3 Since the first report indicating periodontal disease as a potential risk factor for preterm birth in 1996, numerous studies have suggested the link between oral health and adverse pregnancy outcomes. [4][5][6] Adverse pregnancy outcomes is a broad term including preterm birth, preterm premature rupture of membranes, preeclampsia, miscarriage, intrauterine growth retardation, low birth weight, stillbirth, and neonatal sepsis. 3 Preterm birth, defined as birth before 37 weeks of pregnancy, is the leading cause of death among children aged < 5 years. 7 Low birth weight, defined as weight at birth of < 2.5 kg, continues to be a significant public health problem globally, and is associated with a range of short-and long-term consequences. 8 Preeclampsia is a multisystem pregnancy complication characterized by new-onset hypertension with proteinuria, or evidence of systemic disease primarily in the liver and kidneys, after 20 weeks of gestation. 9,10 It is also one of the leading causes of maternal and perinatal mortality and morbidity. 11 Neonatal sepsis refers to an infection involving the bloodstream in newborn infants aged < 28 days and it continues to remain a leading cause of morbidity and mortality among infants, especially in middle-and lowerincome countries. 12 The definition of stillbirth is a baby born with no signs of life at or after 28 weeks of gestation. 13 | EPIDEMIOLOG IC AL E VIDEN CEAccording to a study that summarized the clinical studies from 1996 to April 2020, most studies (232 articles selected, 119 774 participants) in the past 2 decades demonstrate a statistically significant association between periodontal disease and adverse pregnancy outcomes. 14 Similarly, most of the epidemiological studies from 2020 to the present also support a significant effect of periodontal disease on adverse pregnancy outcomes (Table 1). Recent studies continue to investigate the relationship between severity of periodontal disease and adverse pregnancy outcomes, as suggested by an earlier study. 15 A case-control study in 2021 (36 cases, 75 controls) indicated that the prevalence of preterm delivery increased with increasing severity of gingivitis or periodontitis. 16 Likewise, another case-control study in 2020 (60 cases, 120 controls) showed that the severity of periodontitis was significantly associ...