The relationship between cervical dilatation, interleukin-6 and interleukin-8 during term labor

To determine interleukin-6 and interleukin-8 levels in amniotic fluid, retroplacental blood and maternal serum and relate these values with cervical dilatation in term labor.

Prospective study. n=78 healthy women undergoing term cesarean section, divided into four groups: controls, n=42, (elective cesarean section; no contractions, membrane rupture or cervical dilatation); latent labor, n=12, (latent phase labor; cervix <2 cm dilated); established labor, n=12, (active labor, cervix 2-5 cm); advanced labor, n=12, (active labor, cervix >5 cm). Interleukin-6 and interleukin-8 were determined by ELISA (pg/ml), placenta and placental bed biopsy examined histopathologically, and amniotic fluid also microbiologically. Results were expressed as median and ranges or mean and standard deviations, as appropriate. For statistical analysis, Mann-Whitney U-tests or Kruskal-Wallis tests were used as applicable (Statview 4.5). Power and linear regression analyses were performed. p<0.05 was considered significant, p<0.001 highly significant.

Compared with controls, IL-6 and IL-8 increased significantly with cervical dilatation in all compartments tested for almost all labor groups (p<0.05 to p<0.0001). Significant changes were also seen between latent and advanced labor groups in some compartments (p<0.05), but not between established and advanced labor groups. Intrauterine infection was excluded in any of the patients clinically and on histopathological or microbiological analysis of placentae and amniotic fluid.

In term labor without intraamniotic infection, interleukin-6 and interleukin-8 at the fetomaternal interface and in maternal serum rise significantly with cervical dilatation. These cytokines could be used as markers of active labor if vaginal examination is not applicable.