AbstractObjectives: Few large studies have investigated the progression of periodontal conditions during pregnancy in a comprehensive manner. This study aimed to identify clinical factors that were predictive of incidence/progression of periodontal measures in pregnant women adjusting for relevant predictors.Material and Methods: Periodontal examinations were conducted on 891 pregnant women prior to 26 weeks gestational age and within 48 h after delivery. Gingivitis/periodontitis incidence/progression (GPIP) was defined as four plus sites with 2+ mm increase in probing depth (PD) that resulted in PD of at least 4 mm at delivery. Multivariable models including relevant clinical variables and significant covariates were developed.Results: While several clinical measures were significantly associated with the outcome, having 10% of sites with bleeding on probing (BOP) and four plus sites with PD 4 mm (PD4) were the best two predictors of GPIP (odds ratio (OR)=2.8, 95% confidence interval (CI)=1.8–4.2; OR=2.0, 95% CI=1.4–2.9, respectively), adjusting for maternal race, age, enrollment weight, smoking during pregnancy, marital status, food stamp eligibility, and private health insurance. Multivariable models assessed the impact of BOP on the PD4–GPIP relationship. PD4 was significant in the presence of BOP (low BOP OR=1.3, 95% CI=0.5–3.3; high BOP OR=3.0, 95% CI=2.2–4.3).Conclusions: Enrollment BOP and PD4 were significant predictors of PD in pregnant women, however; PD4 is only a predictor with BOP.