Changes Of Interleukin-1 And Interleukin-8 In Amniotic Fluid Before And After Labor In Term Delivery

The mechanism of labor is not fully understood and further research into this important physical process is needed. More and more study shows that cytokines may exert important roles during the process of labor. Successful parturition requires an increase in coordinated uterine contractility together with changes in connective tissue that allow cervical ripening and dilatation .The decidual membrane has a large surface area in contact with the myometrium on one side and the chorion/amnion on the other. Under circumstances of intrauterine infection, decidual macrophages may be involved in preterm labor through the release of inflammatory mediators and prostaglandins (PGs) in the decidual membrane area. During normal labor without clinical infection, decidual cells may increase their output of cytokinesincluding interleukin 1 and 8 which may be related to cervical ripening. The study want to observe potential influences of changes of decidual immune function during labor through changes of IL-1βand IL-8 in amniotic fluid before and after labor in term delivery.The study included 45 primiparae with intact fetal membranes and single pregnancy at 37-41 weeks of gestations undergoing lower transverse cesarean section due to cephalopelvic disproportion or other social excuses. Sample collection was approved by the department of Obstet and Gynecol in the Second Clinical Hospital of Jilin University and Changchun Hospital of Obstet and Gynecol from December 2005 to September 2006. Subjects were excluded for maternal metabolic diseases, systematic or local infection as well as various kinds of Obstetrical complications and syndromes. They were devided into three groups according to the laboring process (group A: before labor; group B: latency phase, cervical dilatated≤3cm; group C : active phase, cervical dilatated>3cm) . Every group consisted of 15 women. Amniotic fluid was obtained during the course of cesarean sectionbefore rupture of membrane. The levels of IL-1βand IL-8 was determined by radioimmunoassay. Excel software was used for statistical analysis and a P-value<0.05 was considered significant. Results: The levels of IL-1βand IL-8 increased with labor progressing, they significantly differed from each other (P<0.05 and P <0.01). It showed positive linear correlation between IL-1βand IL-8 (r=0.914, P<0.01).Cervical ripening is the process by which the cervix changes from a rigid, closed structure designed to retain the uterine contents to one that becomes soft and able to dilate to accommodate the passage of the fetus. The regulation of cervical ripening towards the end of pregnancy is still incompletely understood. Human cervical ripening corresponds to an extensive remodeling of the connective tissue. Cervical softening is the result of digestion of the collagen within the cervix and this is associated with an increase in the water content of the organ. There is increasing evidence that the process of cervical dilatation resembles an inflammatory Response. Increased levels of collagenase and leukocyte elastase have been observed during the final ripening. During cervical ripening, amarked increase of polymorphonuclear cells in decidua, especially neutrophils, has been recorded. These cells synthesis an array of cytokines including IL-1 and IL-8. It is well known that IL-8 is a potent chemotactic activator of neutrophils and it also induces the migration of neutrophils from the vessels to the surrounding connective tissue. These cells participate in the remodeling of the connective tissue by secretin, collagenase and elastase. And increased expression of IL-8 receptors has been found after the initiation of labor. This information supports the role of IL-8 in cervical ripening and partutition. Pharmacologically, the final cervical ripening can be induced by locally applied prostaglandin E2. The advantages of prostaglandins is that they have a relatively specific action, targeting the cervix. IL-1 can induce decidua cells'higher secretion of PGE2. Neutrophil entry into tissue is mediated by a synergistic action between a chemokine such as IL-8 and a vasoactive substance such as PGE2. Moreover, IL-8 acts synergistically with PGE2 as it promotes neutrophil degranulation. Furthermore, PGE2 enhances IL-8 secretion by cervical fibroblasts. Recent researches indicate that IL-1 can enhance corticotrophin-releasing hormone (CRH) secretion. CRH in turn induces PGE2 secretion. Thus IL-1 and IL-8 combine immune system and neuroendocrine system to accelerate cervical ripening through paracrine and autocrine pathways.Changes of IL-1βand IL-8 levels in amniotic fluid before and after labor in term delivery in this study indicate that decidual cells may exert important role during cervical ripening before labor. We do not seek to offer a universal explanation for the onset of labor, rather our hypothesis is intended to provide a framework to stimulate research in this important area. Further studies are in progress to investigate possible agents inducing the release of IL-1 and IL-8 .