Periodontitis and gestational diabetes

Background + Aims

• Periodontitis is a chronic inflammatory disease leading to the destruction of tooth-supporting tissues and eventual tooth loss if untreated. It is highly prevalent worldwide, affecting 10–60% of populations. Beyond oral health, periodontitis contributes to systemic diseases by allowing pathogens (bacteria) and inflammatory mediators to enter the circulatory system, increasing risks for conditions like diabetes mellitus (DM), cardiovascular diseases, and adverse pregnancy outcomes.
• Periodontitis is recognised as a risk factor for DM due to its role in triggering systemic inflammation, impairing glucose metabolism, and damaging pancreatic β-cells. It has also emerged as a potential risk factor for gestational diabetes mellitus (GDM), which affects over 200,000 U.S. pregnancies annually and is linked to serious maternal and neonatal complications. Studies indicate an association between untreated periodontitis and GDM, though the mechanisms and impact of periodontal treatment during pregnancy require further investigation.
• This prospective study compared GDM incidence among pregnant women with and without periodontitis and examined whether receiving periodontal treatment was associated with a lower incidence of GDM.

Materials + Methods

• From January to October 2019, this study recruited adult women with normal glucose levels who were pregnant for the first time with a singleton pregnancy. Enrollment was at 1–4 weeks of gestation, as reported by the authors. Those with systemic diseases (except hypertension) or who had taken medicines within the previous 3-months were excluded.
• Participants were divided into three groups according to their periodontal diagnosis and whether they accepted professional treatment. Treatment allocation was not random:
  • Non-periodontitis (NP)
  • Periodontitis untreated (PU)
  • Periodontitis treated (PT)
• Periodontal examination by dentists assessed plaque index, probing pocket depth (PPD), clinical attachment loss (CAL), and bleeding on probing (BOP). Diagnosis followed the 2017 world workshop classification guidelines (staging and grading).
• Professional treatment in the PT group included supragingival plaque removal, subgingival instrumentation, repeated instrumentation where needed, and supportive periodontal care. The NP and PU groups received oral-hygiene instruction, behavioural advice and regular checks; “untreated” therefore means no clinic-based professional periodontal treatment.
• Gingival crevicular fluid (GCF) and serum for key bacterial species and inflammatory mediators (e.g., CRP, TNF-α, IL-6) were collected and analyzed at 12-16 weeks.
• GDM was diagnosed at 24–28 weeks using an oral glucose tolerance test (OGTT).
• Statistical analysis identified factors influencing GDM incidence using logistic regression and correlation tests.

Results

• This study assessed the relationship between periodontitis and GDM in 3,523 pregnant women.
• Overall, 6.53% of participants developed GDM. Incidence was 4.79% in the NP group (108/2255), 11.21% in the PU group (84/749), and 7.32% in the PT group (38/519). Incidence was significantly lower in the treated than untreated periodontitis group (p = .021). This comparison between self-selected groups does not establish that treatment prevented GDM.
• Compared with women without periodontitis, adjusted odds ratios for GDM were 2.543 (95% CI: 1.612–4.012) in the untreated group and 1.566 (95% CI: 1.064–2.305) in the treated group. These are comparisons with the NP reference group, not a before-and-after treatment change. BMI, chronic hypertension and a family history of diabetes were also associated with higher odds of GDM.
• Higher prevalence of certain bacteria (e.g., P. gingivalis and F. nucleatum) and elevated serum inflammatory markers (CRP, TNF-α, IL-8) were observed in the PU group compared to NP. The treated group also showed lower levels of several bacterial and inflammatory measures than the untreated group; these were between-group comparisons.
• Statistical mediation analyses suggested that P. gingivalis, TNF-α and IL-8 may help explain the association between untreated periodontitis and GDM, but did not establish a causal biological pathway.

Limitations

• This study is limited to a single hospital in China, which may restrict the generalisability of the findings to other populations with different demographic, genetic, and environmental factors.
• The study relied on self-reported data for behaviors like smoking and alcohol consumption, which could introduce reporting bias.
• Women chose whether to receive professional periodontal treatment. This non-random allocation leaves potential selection bias and residual confounding despite statistical adjustment. The study cannot establish that periodontitis causes GDM or that periodontal treatment prevents it.
• There is a lack of stratification by periodontitis severity and the non-quantitative nature of PCR bacterial detection, which may affect the results.
• The lack of longitudinal follow-up after delivery means the long-term impact of periodontal therapy on maternal and neonatal health remains unclear.
• While key inflammatory markers and bacterial species were analysed, the complex interplay between other unmeasured factors, such as diet and microbiome diversity, was not addressed, which could affect the study’s conclusions.

Conclusion

• This study found that periodontitis in early pregnancy is strongly associated with the development of gestational diabetes mellitus (GDM).
• The presence of the bacteria P. gingivalis in the periodontal environment correlates with elevated serum levels of inflammatory mediators like TNF-α and IL-8, potentially playing a key role in this pathological link.
• Professional periodontal treatment was associated with a lower incidence of GDM than no professional treatment, but a preventive effect remains unproven. Further controlled studies and mechanistic research are needed.