OBJECTIVE: The objective of the study was to investigate temporal changes in interleukin-1 receptor antagonist (IL-1ra) in human cervicovaginal fluid (CVF) in term pregnancy and labor. STUDY DESIGN: CVF was collected weekly from 155 multiparous women from 36 weeks' gestation until labor. High vaginal swabs were collected for microbiology assessment. RESULTS: IL-1ra was decreased in spontaneous term labor, compared with 15-21 and 22-28 days from labor, and was significantly lower at 0-7 days, compared with 15-21 days before labor (P .05, 2-way ANOVA). After subdividing the women, IL-1ra concentrations were 6-fold lower in women who had prelabor rupture of membranes at term than women who had spontaneous labor with intact membranes at 8-14 and 15-21 days before labor (P .05, Student t test). IL-1ra concentrations were not affected by the microbial status of the vagina. CONCLUSIONS: The changes in IL-1ra concentrations observed in the CVF may be linked to the remodeling of fetal membranes leading to rupture.

Human labor is characterized by dramatic physiological and structural alterations of the cervix and overlying fetal membranes, leading to myometrial activation and delivery. To investigate the potential mechanism of these changes, we performed 2D PAGE proteomic analysis on serial cervico-vaginal fluid samples obtained from women during late pregnancy and spontaneous labor. We identified 9 protein spots that were significantly altered ( p 0.05) in association with spontaneous term labor. Eight protein spots were definitively characterized by electrospray ion-trap mass spectrometry yielding 7 different proteins: cystatin-A, interleukin-1 receptor antagonist, glutathione S-transferase P, peroxiredoxin-2, thioredoxin, copper-zinc superoxide dismutase, and epidermal fatty-acid binding protein. These proteins are involved in protease inhibition, anti-inflammatory cytokine activity, and oxidative stress defense. These findings may provide an insight into the biochemical processes and timing associated with extracellular matrix remodelling of the cervix, supracervical fetal membranes, and myometrial activation in association with spontaneous term labor. Application of these findings may lead to development of predictive biomarkers of labor onset.