A data monitoring committee will be formed and will include an independent statistician who will conduct the interim analysis. The committee will cease the trial if pre-determined rates of benefit or harm are achieved. Analyses will be conducted on an intention-to-treat basis using tests of proportions and logistic regression that allow for multiple adjustment for covariates. Secondary analyses will be conducted of dose-response of treatment and appropriate comparisons made with women who received periodontal examinations but did not meet eligibility criteria. All hypothesis testing will be two sided and significance will be at the 5% level.