MIAMI BEACH — Unexplained vaginal bleeding and fetal exposure to oral pathogens have been linked individually with spontaneous preterm birth, and new data suggest the presence of both is associated with greater risk than either alone.
Of 660 pregnancies analyzed, 229 (35%) demonstrated fetal exposure to oral pathogens. Pregnancies that demonstrated such exposure were more likely to be in white women, women who had symptomatic bacterial vaginosis, and women who experienced vaginal bleeding, which was the most significant variable associated with oral pathogen exposure (adjusted risk ratio 1.6).
A total of 51 women (8%) in this planned secondary analysis of the Oral Conditions and Pregnancy Study—a prospective observational study of oral health and pregnancy outcomes—delivered before 35 weeks' gestation, Dr. Kim Boggess reported at the annual meeting of the Society for Maternal-Fetal Medicine.
When women with vaginal bleeding were stratified according to whether fetal exposure to oral pathogens occurred, preterm birthrates were significantly higher in those with both factors. Preterm birth occurred in 30% of those with both factors, compared with 8% in those with only vaginal bleeding, 9% of those with only oral pathogen exposure, and 6% of those with neither.
After adjustment for age, race, prior preterm birth, prior elective or spontaneous abortion, bacterial vaginosis, and enrollment weight, the differences remained. The adjusted hazard ratio for spontaneous preterm birth, compared with those with neither risk factor, was 6.4 for those with both factors, 1.9 for those with only vaginal bleeding, and 2.0 for those with only exposure to oral pathogens, said Dr. Boggess of the University of North Carolina at Chapel Hill.
Fetal exposure to oral pathogens was considered to have occurred if umbilical cord serum at delivery demonstrated an immunoglobulin M-positive (IgM-positive) response to at least one of five oral pathogens, she explained.
“Our findings show that antepartum vaginal bleeding is associated with fetal exposure to oral pathogens, and that the combination of fetal exposure to oral pathogens and vaginal bleeding provides the highest risk for premature birth at less than 35 weeks,” Dr. Boggess said.
“We think that vaginal bleeding may in fact be an effect measure modifier of fetal exposure to oral pathogens.”
Unexplained vaginal bleeding may be one of the mechanisms of fetal exposure to oral pathogens during pregnancy, but further study is needed to determine whether vaginal bleeding is the cause or the effect of fetal exposure to oral pathogens, she said.
The findings also suggest that clinical determination of periodontal disease is a poor marker for fetal exposure to oral pathogens, she noted.