A disproportionate increase in IL-1β over IL-1ra in the cervicovaginal secretions of pregnant women with alteredvaginal microflora correlates with preterm birth

Objective This purpose of this study was to investigate the association between vaginal microflora, concentrations of interleukin-1β (IL-1β), and its natural receptor antagonist (IL-1ra) in the cervicovaginal discharge, and spontaneous preterm birth. Study design Vaginal samples collected at 18 to 22 weeksʹ gestation from 207 women were analyzed to study qualitative and quantitative microbiologic aspects of vaginal microflora and IL-1β and IL-1ra concentrations. Results Among women colonized with anaerobic Gram-negative rods and/or Gardnerella vaginalis, an elevated IL-1β concentration, or a diminished IL-1ra:IL-1β ratio were associated with preterm delivery. A cut-off IL-1ra:IL-1β ratio of <8,632:1 optimally discriminated the subjects with subsequent spontaneous preterm deliveries from subjects who delivered at term, with a sensitivity of 78%, specificity of 51%, positive predictive value of 21%, and negative predictive value of 95%. Conclusion A disproportionate increase in IL-1β over IL-1ra in response to vaginal colonization with anaerobic Gram-negative rods and/or G. vaginalis at 18 to 22 weeksʹ gestation is associated with spontaneous preterm delivery.