Polymorphism in intron 2 of the interleukin-1 receptor antagonist gene, local midtrimester cytokine response to vaginal flora, and subsequent preterm birth

This study investigated the association between polymorphism in intron 2 of the interleukin-1 receptor antagonist gene, midtrimester vaginal microflora, vaginal interleukin receptor antagonist and interleukin-1β levels and subsequent spontaneous preterm birth. Vaginal samples from 212 women, collected at 18-22 weeks' gestation, were analyzed for the polymorphism in intron 2 of the interleukin-1 receptor antagonist gene by polymerase chain reaction, qualitative and quantitative vaginal microflora, and interleukin-1β and interleukin-1ra concentrations by enzyme-linked immunosorbent assay. Pregnancy outcome data were subsequently obtained. Carriage of intron 2 of the interleukin-1 receptor antagonist allele 2 (IL1RN∗2) was associated with an elevated vaginal pH in black (P < .001) and white (P=.005) women, a reduced interleukin-1β response to anaerobic Gram-negative rods and/or Gardnerella vaginalis (P < .01), and a decreased rate of spontaneous preterm deliveries (6% versus 18%, P=.02). In black women, IL1RN∗2 carriage was associated with increased anaerobic Gram-negative rods, Mycoplasma, and Peptostreptococci and decreased Lactobacilli colonization. IL1RN∗2 carriage was associated with a blunted proinflammatory interleukin-1β response to abnormal vaginal flora. This property may decrease susceptibility to infection-related preterm birth.