Maternal serum levels of interleukin-6 and clinical characteristics of normal delivery at term

Background. The objective of the present study was to study participation of cytokines and cytokine inhibitors during the process of normal parturition, as assessed by maternal serum levels of interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor (TNF) and soluble tumor necrosis factor receptors (sTNFRs, p55 and p75). Materials and methods. Twenty-six healthy women in normal term labor were observed during parturition and until 2 h post partum. Serum was sampled every 2 h, and an evaluation of strength and frequency of contractions was performed at the time of sampling. Concentrations of IL-1, IL-6, TNF, p55 and p75 were analyzed, and non-parametric tests were used to study whether any relationship existed between the serum analyzes and the clinical characteristics of parturition. Results. There was a significant association between the strength of contractions and the levels of IL-6 and p55. In addition, IL-6 concentrations and frequency of contractions were correlated. Maternal serum levels of IL-6 and p55 were highest 2 h post partum. TNF activity was detected in samples from nine women, whereas IL-1 was not found in any sample. Conclusions. The present study suggests a role of IL-6 and p55 in normal labor. However, as women being studied already were in labor, the study does not allow any conclusions whether observed changes in IL-6 and p55 levels have a causal relation to the process of labor or if changes are secondary effects of the process itself.