Periodontal infection and preterm birth: successful periodontal therapy reduces the risk of preterm birth.

OBJECTIVE This study tested the hypothesis that successful periodontal treatment was associated with a reduction in the incidence of spontaneous preterm birth (PTB). DESIGN This was a randomised, controlled, blinded clinical trial. SETTING Hospital outpatient clinic. POPULATION Pregnant women of 6-20 weeks of gestation were eligible. METHODS Of 322 pregnant women with periodontal disease, 160 were randomly assigned to receive scaling and root planing (SRP, cleaning above and below the gum line), plus oral hygiene instruction, whereas the remaining 162 received only oral hygiene instruction and served as an untreated control group. Subjects received periodontal examinations before and 20 weeks after SRP, and were classified blindly according to the results of treatment into two groups: successful ('non-exposure') and unsuccessful ('exposure') treatment. Groups were compared using standard inferential statistics; dichotomous variables were compared using the chi-square test or logistic regression. Results are presented in terms of odds ratios. MAIN OUTCOME MEASURE The main outcome measure was spontaneous preterm birth before 35 weeks of gestation. RESULTS No significant difference was found between the incidence of PTB in the control group (52.4%; n = 162) and the periodontal treatment group (45.6%; n = 160) (P < 0.13, Fisher's exact test). The incidence of PTB was compared within the periodontal treatment group, considering the success of therapy. A logistic regression analysis showed a strong and significant relationship between successful periodontal treatment and full-term birth (adjusted odds ratio 6.02; 95% CI 2.57-14.03). Subjects refractory to periodontal treatment were significantly more likely to have PTB. CONCLUSIONS A beneficial effect on PTB may be dependent on the success of periodontal treatment.