During pregnancy, dental plaque-induced gingivitis prevalence and subsequent risk of periodontal disease increases substantially as a consequence of both inadequate oral hygiene and changes in sex steroid hormone levels. Although maternal periodontal disease has been associated with adverse pregnancy outcomes, including spontaneous preterm birth, previous clinical trials involving mechanical debridement (e.g., scaling and root planing) to remove plaque biofilm have not yielded decreased rates of preterm birth. We hypothesized that an advanced oral hygiene program, including an antibacterial regimen coupled with a power toothbrush and hygiene instruction, may improve the periodontal milieu and reduce the rate of spontaneous preterm birth. Therefore, we conducted a clinical trial of obstetrical patients with moderate-to-severe gingivitis who were randomized to an advanced oral hygiene program versus usual oral hygiene care, and the primary obstetric outcome compared between the treatment groups was gestational age at delivery. Obstetrical patients with singleton pregnancies between 8 and 24 weeks gestation were screened by trained dentists at two clinical sites for moderate-to-severe gingivitis (more than 30 intra-oral sites with gingival bleeding on probing). Eligible participants were randomized to an advanced oral hygiene regimen, including antibacterial mouth wash, dental floss, antibacterial toothpaste, a power toothbrush, and intensive oral hygiene education versus standard oral home care instructions and regimen. The primary obstetric outcome assessed was gestational age at delivery. The overall primary (dental) outcomes were gingival index, bleeding sites, and pocket depth (reported elsewhere). Secondary obstetric outcomes included birthweight and incidence of preterm birth at <37 weeks. Regression models were utilized and included factors such as treatment group, gestational age at enrollment, preterm birth history, and potential markers of health disparities (i.e., education, employment status). A total of 817 obstetrical patients underwent dental screening at the two sites, 789 were identified with moderate-to-severe gingivitis, 746 were randomized, and birth outcomes were available for 613 of the study participants. The gestational age at delivery was two days earlier in the control group (p=0.040), but the clinical significance of this finding was limited (39.13 vs 38.85 weeks). Overall rates of spontaneous preterm birth <37 weeks and <34 weeks were not statistically different between the two treatment groups (7.0% advanced oral hygiene regimen versus 10.3% controls, OR=1.63 (0.90, 3.00), p=0.11; and 2.3% versus 3.9%, OR=1.88 (0.71, 4.98), p=0.20, respectively). However, we observed lower rates of spontaneous preterm birth among unemployed participants with less favorable socioeconomic status (4.7% advanced oral hygiene regimen versus 16.0% controls, OR=4.04 (1.34, 15.12), p=0.01). An advanced oral hygiene program may reduce the risk of spontaneous preterm birth among pregnant patients with moderate-to-severe gingivitis and health disparities. This is the same group that may be at highest risk of poor dental hygiene and preterm birth.