Maternal periodontal disease is a highly prevalent condition that has been studied extensively in relation to adverse pregnancy outcomes, including preterm delivery, preeclampsia, and low birth weight. Investigators speculate that hematogenous transport of bacteria and/or pro-inflammatory mediators from sites of periodontal infection into the placenta, fetal membranes, and amniotic cavity induces pathological processes that lead to these adverse outcomes. Preliminary observational studies supported this hypothesis, but more recent work by our group and others do not demonstrate an increased risk of adverse pregnancy outcomes among women with periodontal disease, and most randomized trials fail to demonstrate improved perinatal outcomes following treatment of periodontal disease in pregnancy.