Antepartum vaginal bleeding, fetal exposure to oral pathogens, and risk for preterm birth at <35 weeks of gestation

Objective The purpose of this study was to determine the risks for fetal exposure to oral pathogens and the relationship between vaginal bleeding and fetal exposure in preterm birth risk. Study design An analysis of prospectively collected data for the longitudinal Oral Conditions and Pregnancy Study was conducted. Maternal factors that potentially were associated with fetal exposure to oral pathogens (defined as detection of umbilical cord serum Immunoglobulin M to 1 of 5 oral pathogens) were examined, and the role of vaginal bleeding and fetal exposure to oral pathogens in preterm birth risk was explored. Preterm birth was defined as delivery at <35 weeks of gestation. An adjusted relative risk (95% CI) for fetal exposure was calculated. Adjusted hazard ratios (95% CI) were calculated for preterm birth among women whose data were stratified by the presence/absence of bleeding and/or fetal exposure to oral pathogens. Results There were complete data for 661 women; 230 women (34.8%) with and 431 women (65.2%) without fetal exposure to oral pathogens. In multivariable analysis, first- or second-trimester bleeding and white race were associated significantly with fetal exposure to oral pathogens (adjusted relative risk, 1.8 [95% CI, 1.3-2.5] and 1.3 [95% CI, 1.1-1.7], respectively). The adjusted hazard ratio for preterm birth among women with first- or second-trimester bleeding and fetal exposure to oral pathogens was 6.4 (95% CI: 2.6-16.0). Conclusion Vaginal bleeding is associated with fetal exposure to oral pathogens, which increases preterm birth risk. Whether bleeding is the cause of or result of fetal exposure to oral pathogens remains to be determined.