Cytokine concentrations in amniotic fluid and the lower uterine segment: Correlation with labor and cervical dilatation

Objective: To evaluate the relationship between cytokine levels in the amni otic fluid and lower uterine segment, cervical dilatation, and duration of labor. Methods: In 29 patients undergoing cesarean delivery at term we obtained a specimen of amniotic fluid and a tissue biopsy from the lower uterine segme nt. Concentrations of interleukin-6 (IL-6) and IL-8 were measured by enzyme immunoassays. Cervical dilatation was < 2 cm, 2 to <4 cm, 4 to 6 cm, and > 6 cm in 10, 9, 5 and 5 patients, respectively. Duration of labor was 0, > 0 to 6, > 6 to 12, > 12 to 24, and > 24 h in 10, 4, 8, 5 and 2 patients, re spectively. The data were analyzed with the Wilcoxon two-sample test. Results: In the amniotic fluid IL-6 increased markedly to 10118 pg/mg (p < 0.02) at a cervical dilatation of greater than or equal to 2 - < 4 cm. In c ontrast the strongest increase in IL-8 was seen at a dilatation of > 6 cm ( 16799 pg/mg, p = 0.003) and the first significant increase of IL-8 occured at a dilatation of 4-6 cm. Both cytokines increased further at > 6 cm of di latation. In the lower uterine segment cytokine levels increased significan tly only at a dilatation of 4 - 6 cm and stayed stable thereafter. There wa s no significant correlation between cytokine increases in the amniotic flu id and the lower uterine segment. In contrast to IL-8, IL-6 levels correlat ed with the duration of labor after 6 hours and longer (Pearson correlation coefficient 63 %). Conclusions: During labor IL-6 levels increase in the amniotic fluid before the lower uterine segment. This suggests that IL-6 may be more important f or the initiation of labor than for degradation processes in the lower uter ine segment. The IL-8 peak later in labor suggests a role for this cytokine for neutrophil invasion of the lower uterine segment.