Original Article The Interplay of the Interleukin 1 System in Pregnancy and Labor

This work assessed the temporal coexpression of interleukin 1 (IL-1) and its inhibitor, IL-1 receptor antagonist (IL-1ra), in the cervi-covaginal fluid (CVF) beyond 24 weeks gestation including women in spontaneous term labor. Two cohorts of women were recruited at 24 to 35 weeks ’ gestation (n 65) and in late pregnancy (>36 weeks ’ gestation; n 88). The CVF was serially collected either every 4 weeks between 24 and 35 weeks ’ gestation (n 123 samples) or weekly during late pregnancy (n 240 samples). The IL-1 and IL-1ra were quantitated by enzyme-linked immunosorbent assay, and the effect of vaginal microflora and unprotected sexual intercourse were also investigated. The IL-1b and IL-1ra remain unaltered between 24 and 35 weeks ’ gestation. At late pregnancy, IL-1a and b concentrations peak at 4 to 14 days prior to labor onset, while IL-1ra decreases with approaching spontaneous term labor (P <.05, 2-way analysis of variance). The IL-1 and IL-1ra were significantly correlated (P <.001, Pearson r). A combined bio-marker model of IL-1a, IL-1b, and IL-1ra can predict term labor with 86 % sensitivity and 92 % specificity. This study indicates a shifting inflammatory balance in the gestational tissues prior to labor onset